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Tomkins,  Queen's  College,  Liverpool. 

3.  BUILDING  CONSTRUCTION.     By  R.  Scott  Burn,  C.E. 

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POPULAE  PHYSIOLOGY. 


A    MANUAL 


OF 


POPULAR  PHYSIOLOGY: 


BEING 


AX  ATTEMPT  TO  EXPLAIN  THE  SCIENCE  OF  LIFE 
IN  UNTECHNICAL  LANGUAGE, 


BY 

HENKY  LAWSON,   M.D. 


NEW  YORK: 

G.    P.    PUTNAM'S    SONS. 
1873. 


(/I 


2> 


BIOLOGY 
LIBRARY 

(i 


TO 

E.  V. 

IN    REMEMBRANCE    OF    MUCH    KINDNESS, 

Cjjfa  Tilth  VtSmt 

IS  AFFECTIONATELY   DEDICATED 
BY 

THE  AUTSOE 


W 


258159 


PREFACE. 


IN  the  following  chapters  it  has  been  attempted  to  set  before  the 
public,  in  as  easy  a  style  as  possible,  the  more  interesting  results 
of  physiological  research.  Dry  details  have  been  avoided,  except 
where  the  nature  of  the  subject  rendered  their  introduction  in- 
evitable ;  whilst  the  grand  general  principles  and  laws  of  the  Science 
have  been  enunciated  in  language  as  devoid  of  technicality  as  it 
seemed  advisable  to  employ.  In  no  case  has  truth  been  distorted 
to  attain  simplicity ;  and  withal  the  volume  (it  is  hoped)  embodies 
the  latest  discoveries  in  the  branch  of  knowledge  upon  which  it 
treats. 

This  work  is.  not  addressed  to  the  man  of  Science ;  nor  is  it 
supposed  that  students  proceeding  to  degrees  in  Medicine  will 
devote  much  attention  to  it.  There  is,  however,  a  large  class, 
in  which  the  author  is  happy  to  say  he  once  ranked,  that,  although 
not  professedly  scientific,  is  glad  to  profit  by  the  gleanings  from 
the  great  field  of  Biology.  Eor  it,  this  little  volume  has  been 
written ;  and  if  it  inspires  even  one  person  with  a  desire  to  embrace 
the  cause  of  Science,  the  Author  will  be  amply  satisfied. 

In  order  that  those  who  wish  to  pursue  the  subject  as  a 
specialise  may  do  so  without  difficulty,  the  names  of  the  more  im- 
portant treatises  on  Physiology  and  on  other  sciences  which  relate  to 
it  have  been  appended  to  the  volume.  Should  other  references  be 
needed,  they  may  be  found  in  the  Medico-Chirurgical  and  Natural 
History  Reviews,  the  Archives  of  Medicine,  and  the  valuable 
bibliographical  compilation  of  Professor  Carus. 

There  is  an  old  and  familiar  proverb  regarding  the  strangulation 
of  that  member  of  the  canine  genus  which  has  through  some  mis- 


Vlll  PREFACE. 

chance  been  deprived  of  its  fair  reputation.  The  Author  has  no 
inclination  to  institute  unseemly  analogies ;  nevertheless  it  appears 
to  him  that,  to  the  minds  of  some  English  savans,  popular  Science 
merits  the  fate  of  the  unlucky  being  to  which  he  has  alluded.  He 
regrets  that  such  a  state  of  things  exists,  and  hopes  that  ere  long 
those  who  so  zealously  decry  untechnical  Science,  on  the  principle 
that  half  a  loaf  is  not  better  than  no  bread,  may  be  relieved  of  the 
painful  hallucination  under  which  they  now  labour.  Are  we  to 
assume  that  because  a  man  is  unable  to  read  "  Faust "  in  the 
language  of  Goethe,  he  is  therefore  unwarranted  in  enjoying  a 
translation  of  that  sublimest  of  German  writings  ? 

In  conclusion,  the  author  would  remark  that  in  the  footsteps  of 
BREWSTER,  GOSSE,  JONES,  HUXLEY,  and  LANKESTER,  who  have  all 
written  for  the  people,  no  man  need  blush  to  follow. 

QUEEN'S  COLLEGE,  BIRMINGHAM, 
June  lOtf,  1863. 


POPULAE   PHYSIOLOGY. 


CHAPTER  I. 

INTRODUCTION. 

Kelation  of  other  Sciences  to  Physiology — Three  kinds  of  Natural  Objects 
—Distinction  between  Animals  and  Plants — Nature  of  an  Element — 
Action  of  Vegetables  on  the  Earth  and  Air — Dependence  of  Animals 
upon  the  Plant -World — Passage  of  Fluids  through  Membranes — 
Osmose — Endosmose — Exosmose. 

IN  order  to  study  with  advantage  the  higher  departments  of 
Physi9logical  Science  it  is  almost  essential  that  one  should  be 
acquainted  with  the  general  principles  of  Anatomy,  Zoology,  Botany, 
Chemistry,  and  Experimental  Physics  ;  but  as  in  the  following  pages 
the  rudiments  of  Physiology  have  alone  found  a  place,  it  will  not  be 
necessary  for  the  reader  to  possess  a  knowledge  of  these  compre- 
hensive and  difficult  branches  of  learning.  However,  since  it  is 
impossible  that  any  clear  description  of  the  processes  gone  through 
by  the  human  body,  could  be  given  without  some  reference  to  other 
sciences,  I  shall  ^devote  this  chapter  to  a  few  remarks  on  collateral 
information  bearing  on  Physiology. 

A  moment's  reflection  will  suffice  to  convince  anyone  that  each 
object  by  which  he  is  surrounded  is  one  of  three  kinds  :  thus,  let  the 
reader  suppose  himself  in  a  balloon,  some  thousand  feet  above  the 
earth's  surface,  and  on  looking  down,  say,  in  the  most  general  way 
possible,  how  many  sorts  of  things  he  sees ;  or,  let  him  imagine  that 
he  has  got  to  arrange  the  various  objects  he  beholds  in  such  a  manner 
that  there  shall  be  but  three  divisions,  and  yet  that  all  the  contents 
of  each  division  may  be  of  the  same  description,  and  I  have  no 
doubt  he  will  observe,  that  the  three  groups  are  minerals,  vegetables, 
and  animals.  So  far  so  good ;  having  bundled  up  the  different  materials 
in  this  way,  we  shall  leave  the  first  to  the  chemists  and  geologists, 
whilst  our  friends  the  botanists  shall  share  the  vegetables  with  us, 
and  the  zoologist  shall  classify  the  animals,  so  that  we  shall  have  no 
difficulty  in  pitching  upon  the  beasts  we  may  require  for  our  experi- 
ments. If  it  be  asked,  how  are  we  always  to  decide  whether  an 
object  belongs  to  any  particular  class ;  or  how  shall  we  maintain 
our  rights,  and  prevent  those  speculative  ay  and  combative  fellows, 
the  geologists,  from  trespassing  upon  our  premises?  I  must  reply 
that  here,  even  in  the  present  day,  we  are  "in  a  fix,"  and  not- 

B 


2  POPULAR  PHYSIOLOGY. 

withstanding  that  loud-sounding  essays  have  been  written,  and 
terrific,  jaw-breaking  Greek  names  have  been  coined,  we  have  yet 
arrived  at  very  little  improvement  on  the  statement  of  Linnaeus,  that 
"  stones  grow,  vegetables  grow  and  live,  and  animals  grow,  live,  and 
feel."  There  are  certain  other  peculiarities  upon  which  I  shall  not 
dwell,  as  they  are  of  little  interest  to  the  general  reader,  who,  I  doubt 
not,  would  laugh  heartily  at  the  notion  of  mistaking  a  cabbage  for 
an  oyster,  or  this  latter  for  a  common  fire-brick ;  yet  smile  though 
he  may,  I  can  tell  him  that  it  is  a  matter  of  no  small  trouble  to 
prove  that  a  sponge  is  not  a  vegetable,  though  Decent  investigations 
have  discovered  in  the  sponge  a  nearer  relation  to  man  than  was 
dreamed  of  when  it  served  the  purpose  of  completing  our  shaving 
operations  some  years  since.  Physiology  has  to  do  with  both  plants 
and  animals,  but  it  does  not  treat  of  their  forms  or  structure,  these 
belonging  properly  to  the  sciences  of  morphology  and  anatomy, 
which  lend  us,  as  it  were,  a  helping  hand  now  and  then ;  it  teaches 
us  how  the  complex  machinery  of  these  beings  acts,  in  a  word  it 
deals  with  their  functions.  Animals  could  not  continue  to  exist 
without  plants,  for  two  reasons :  firstly,  because  they  would  be  deprived 
of  food ;  secondly,  because  they  would  be  suffocated ;  now  it  is  only 
by  calling  in  the  assistance  of  chemistry  that  we  can  be  made  to 
understand  these  facts.  Chemists  have  carefully  examined  almost 
all  mineral  substances,  and  have  found  that  these,  no  matter  how 
different  they  may  be  from  one  another,  are  composed  of  a  certain 
number  of  simple  materials,  which  cannot  be  subdivided  into  any 
others ;  each  simple  substance  they  term  an  element,  and  elements 
may  be  combined  artificially  to  form  minerals.  This  may  be  difficult 
to  appreciate  at  the  outset,  but  by  comparing  the  elements  of  the 
chemist  with  the  letters  of  the  alphabet  the  difficulty  will  vanish ; 
thus,  each  word  when  analysed  will  be  found  to  consist  of  a  series 
•of  elementary  parts,  or  letters,  which  may  again  be  reconstructed 
into  words.  Words  in  this  case  represent  minerals ;  letters  take  the 
place  of  elements.  Numerous  as  are  the  varieties  of  mineral  com- 
pounds which  lie  scattered  over  the  globe,  we  find  that  the  elements 
which  constitute  them  are  but  seventy  or  thereabouts  in  number ; 
in  fact,  the  mineral  alphabet,  so  to  speak,  contains  seventy  letters  : 
but  oh  !  how  manifold  are  the  words,  how  complex  the  idioms,  how 
difficult  but  withal  how  sublime  the  grammar  and  translation ! 

I  fancy  the  reader  can  soon  perceive  in  their  full  force  the  advan- 
tages of  plants  to  us,  which  I  alluded  to  above. 

Vegetables,  like  animals,  are  supplied  with  earth,  water,  and  air, 
and  from  these  they  manufacture  (if  that  term  may  be  so  employed) 
the  food  on  which  animals  subsist ;  they  possess  a  power  of  cpmposing, 
which  is  denied  to  animals ;  and,  to  carry  our  alphabet  simile  still 
further,  plants  hold  the  same  position  with  regard  to  animals  that  a 
man  who  can  read  and  write  holds  with  reference  to  a  child  who 
has  only  learned  his  letters ;  the  first  in  each  instance  can  form  new 
combinations, — the  man  new  words,  the  plant  new  compounds.  It 
is  of  importance  to  recollect  that  plants  cannot  combine  any  set  of 
elements  but  only  a  limited  quantity.  To  illustrate  what  I  have 


INFLUENCE  OF  PLANTS. 


just  mentioned,  let  us  imagine  a  plant  to  be  supplied  with  earth,  air, 
and  water,  and  it  will  cause  the  following  changes  in  these  latter: — 
"  Oxygen  . .  Set  free. 


Air  is  composed  of 


Nitrogen 


Water 


Earth 


Food 


Mineral  matter 


>  Plant. 


Carbon 
(Oxygen  .. 
I Hydrogen 
'  Lime 
Potash  .. 
Flint  . . 
Common  salt,  &c.  ; 
The  vegetable  has  drawn  into  it  certain  minerals,  has  made 
some  of  the  gases  of  the  air  unite  with  water  to  form  a  new  com- 
pound which  may  serve  us  for  food,  and  in  doing  so  has  set  free  a 
gas  called  oxygen,  which  goes  back  again  to  the  atmosphere ;  at  least 
by  n9t  appropriating  it,  it  has  allowed  it  to  remain  behind ;  and 
this  is  of  the  utmost  moment,  for  it  is  upon  oxygen  that  animals 
depend  —  as  I  shall  show  hereafter  —  for  the  purification  of  their 
blood ;  whilst  carbon,  which  the  vegetable  world  has  abstracted,  was, 
when  in  the  air,  under  a  most  poisonous  form,  and,  if  allowed  to  remain 
there,  would  have  proved  highly  detrimental  to  animal  existence. 
To  complete  the  balance,  I  must  observe  that  animals  are  perpetually 
vitiating  the  atmosphere,  by  pouring  into  it  from  their  lungs  carbon, 
in  the  gaseous  form  I  have  referred  to ;  thus,  what  the  animal  rejects 
the  plant  feeds  on,  and  what  the  plant  leaves  the  animal  respires : 
this  the  diagram  beneath  will  render  explicit : — 

Air. 


Plant. 


Animal. 


The  nitrogen  plays  the  part  of  water  in  adulterated  milk  —  only 
dissolves  and  dilutes.  The  plant  allows  the  oxygen  to  ascend  from 
it,  whilst  it  attracts  the  carbon ;  the  animal  allows  the  carbon  to 
proceed  from  it,  and  absorbs  the  oxygen.  This  must  not  be  looked  on 
as  an  accurate  and  precise  explanation,  but  conveys,  in  a  rough  way, 
an  idea  ot  the  process,  which,  were  it  detailed  at  full  length,  and 
with  consideration  of  recent  researches,  would  be  too  Buzzing  and 
complicated  for  these  pages. 

It  must  not  be  supposed,  from  the  foregoing  remarks,  that  animals 
can  produce  no  alteration  in  vegetable  compounds.  Though  inca- 
pable of  building  up  new  structures  from  element*,  they  can  bring 

B  2 


4  POPULAR  PHYSIOLOGY. 

about  changes  in  food  submitted  to  them ;  but  of  this  I  shall  say 
more  in  the  proper  place.  _ 

Concerning  the  application  pi  experimental  physics  to  the  study  of 
Physiology,  I  need  only  mention  one  circumstance  with  which  some 
of  my  readers  may  not  be  conversant,  viz.,  when  a  thick  fluid, 
contained  in  a  bladder,  is  immersed  in  a  fluid  which  is  thinner, 
both  fluids  pass  through  the  membrane  towards  each  other,  the  thick 
one  passes  out  to  the  thin  one,  and  vice  versa  (tig.  2 A).  Thus,  if  a 
strong  solution  (d)  of  sugar  be  enclosed  in  a  tube  (e,  /),  whose 
bottom  (b,  c)  is  an  animal  membrane,  and  this  be  plunged  into  a 
vessel  of  water  (a),  it  will  be  found,  after  a  while,  that  some  of  the 
sugar  has  passed  out,  and  a  portion  of  the  water  in ;  to  this  per- 
meation the  name  of  osmose  (psmos,  a  plant)  has  been  applied,  the 
Sassage  outwards  being  termed  exosmose,  and  that  towards  the  inner 
uid  endosmoge  (lig.  2B}. 

The  laws  of  mechanics  and  hydraulics  we  shall  find  also  applicable 
to  some  of  the  duties  performed  by  parts  of  the  animal  body, 
though  it  would  be  out  of  place  to  enter  upon  that  portion  of  the 
subject  here. 


Fig.  2A. 


Fig.  2s. 


THE   HUMAN   SKELETON. 


CHAPTER   II. 

Method  of  examining  Man's  Mechanism— Comparison  between  a  Watch 
and  the  Human  Frame — General  plan  of  the  Skeleton — Protective 
Bones,  and  Locomotive  Bones — Vertebrae — Ideal  Vertebra  or  Model 
— The  Limbs — Resemblances  between  the  Arms  and  Legs — Soft  parts 
of  the  Body — Division  of  the  Trunk  into  two  portions  :  Chest  and 
Belly— Position  of  the  Great  Viscera  :  Lungs,  Heart,  Liver,  &c. 

How  hard  it  would  be  to  form  any  adequate  conception  of  the 
beauty  of  the  mechanical  arrangement  observable  in  a  watch,  if  the 
various  wheels,  springs,  and  appliances  which  compose  it  had  been 
previously  separated  from  each  other,  and  given  to  us  altogether  in 
chaotic  confusion.  What  an  imperfect  geographical  knowledge  we 
should  possess,  did  we  huddle  together  the  names  of  the  cities',  in 
every  nation,  without  regard  to  their  position  and  distance  from  eacli 
other.  These  questions  show  us  the  necessity  of  taking  a  general 
survey  of  the  complex  piece  of  mechanism  we  are  about  to  examine, 
before  we  take  it  bit  by  bit  asunder.  When  we  gain  a  notion  of  the 
geography  of  the  man-world,  we  shall  then  examine  each  particular 
region ;  and  we  can  do  so  with  more  ease,  for  in  human  mechanics, 
as  in  the  watch,  every  little  structure  is  in  some  way  dependent  on 
the  other ;  all  parts  are  bound  firmly  together,  and  if  one  portion  of 
the  apparatus  be  removed,  the  entire  combination  is  seriously  aifected, 
and  the  heart,  that  human  " balance"  indicates  but  too  clearly  that 
life,  the  main-spring  of  the  system,  has  exhausted  its  hitherto  accumu- 
lated force. 

In  the  watch  the  wheels  and  springs  are  supported  by  the  frame- 
work, and  protected  by  the  cover ;  so  in  man  also  have  we  the  frame- 
work in  the  bony  skeleton,  and  the  cover  in  the  skin,  or,  as  it  is  more 
usually  called,  the  integument ;  to  perfect  the  analogy,  we  have  only 
to  disc9\Ter  something  similar  to  the  movements  of  the  chronometer, 
and  this  is  no  difficulty ;  all  those  portions  of  man's  body  which 
have  a  set  office  to  perform,  and  which  are  termed  organs,  are  actually 
thejiuman  "movements"  if  we  may  so  designate  them. 

Nothing  can  show  more  fully  than  the  skeleton  of  man,  the  neces- 
sity for  admitting  the  existence  of  a  Creator;  the  wonderful  design 
which  it  exhibits,  and  the  admirable  dovetailing  of  means  to  end ; 
the  granclness  of  the  general  plan,  and  withal,  the  extraordinary 
adaptation  of  every  individual  portion  to  the  wants  and  requirements 
of  the  being,  point' to  a  supreme  First  Cause,  of  whose  infinite  intelli- 
gence we  can  form  but  a  meagre  and  imperfect  notion  at  best.  _  The 
human  skeleton  may  be  divided  into  two  parts ;  first,  that  which  is 
protective,  serving  to  enclose  and  screen  from  injury  the  important 
organs  ;  second,  that  which  is  added  to  enable  the  creature  to  move 
from  place  to  place,  and  to  provide  itself  with  food.  The  one  I  shall 
term  the  protective,  the  other  the  locomotive  division.  In  treatises 


Frontal  Bone 


Parietal  Bone. 


Orbit 


Lower  Jaw 


Leg-bones 


Fig.  3. — Human  Skeleton 


IDEAL  AND  REAL  VERTEBBJE.  7 

on  human  anatomy  it  is  usual  to  state  that  so  many  bones  are  in  the 
skeleton,  and  then  to  begin  a  dry,  technical  description  of  each  ;  this 
is  puzzling  enough  to  the  unlucky  medical  tyro,  and,  as  a  matter  of 
course,  would  be  still  more  so  to  the  general  reader,  so  we  shall  not 
follow  a  scheme  of  that  kind. 

If  I  were  to  come  across  a  savage,  entirely  ignorant  of  the  nature 
and  form  of  the  houses  we  civilized  people  live  in,  and  I  wished 
to  convey  to  him  some  idea  of  the  character  of  our  domestic 
architecture,  think  you  I  should  give  him  a  lucid  conception  by  com- 
mencing in  this  style :  On  either  side  of  the  hall  is  a  sitting-room, 
two  more  in  the  rear ;  there  is  a  kitchen,  a  scullery,  and  there  are 
four  bedrooms,  &c. ;  and  then  enlarge  upon  the  size  of  the  apart- 
ments, their  floorings,  windows,  papering,  and  so  forth  ?  Certainly 
not.  I  should  begin  with  the  simplest  form  of  house,  thus  showing 
him  the  general  plan,  and  then  I  should  lead  him  step  by  step  to 
more  complex  forms ;  and  so  he  would  have  some  appreciation  of 
what  I  meant  to  convey.  Now  this  is  just  what  I  mean  to  do  in 
giving  the  "  estimate "  of  man's  architecture ;  we  must  first  glance 
at  the  plan,  and  afterwards  seriatim  take  up  the  details.  The  pro- 
tective division  of  the  bony  framework  is  much  less  complicated 
than  it  seems,  and,  no  matter  what  its  length  or  breadth,  is  made  up 
of  a  chain  of  parts,  which  are  large  or  small,  to  suit  particular  pur- 
poses, but  which  are  all  constructed  on  one  plan.  I  do  not  wish  the 
reader  for  a  moment  to  suppose  that  the  Creator  had  that  plan  before 
Him  "in  the  beginning."  That  would  be  going  a  little  too  far;  but. 
to  our  minds,  they  are  reducible  to  one  kind,  just  as  we  may  say  all 
lighthouses  are  built  upon  a  common  plan— viz.,  a  means  of  producing 
a  light-signal,  and  a  means  of  erecting  this  signal  so  that  it  may  be 
seen.  The  common  fire  beacon  of  remote  seaside  villages,  and  the 
complex  Eddystone,  have  for  us  certain  things  in  common, 
so  that  we  picture  to  our  minds  an  ideal  lighthouse,  and 
modify  it  to  suit  our  pleasure,  without  troubling  ourselves 
to  consider  whether  the  architects  possessed  our  plan  or 
not.  In  a  loose  way,  we  may  look  upon  the  protective 
skeleton  as  being  constituted  of  the  Back-bone,  Chest, 
and  Skull ;  but  when  we  come  to  consider  each  of  these  Fi?>  4< 
in  its  turn,  we  shall  find,  as  I  mentioned,  that  it  is  composed  of 'a 
chain  of  bones,  resembling  each  other 
strongly,  and  which  I  shall  call  vertebra 
(fig.  4).  These  are — if  I  may  be  excused 
the  comparison— the  bricks  of  the  edifice, 
and,  like  these  latter,  have  a  bit  lopped  off 
now  and  then  to  suit  a  special  end. 

Before  we  cast  our  eye  over  the  different 
vertebrae,  let  us  look  at  our  model  (fig.  5). 

It  consists  of  a  solid  centre,  or  oody 
(c),  to  which  is  conjoined,  on  the  upper 
part,  a  triangular  arch  (#),  prolonged  into 
a  spine,  and  from  whose  lower  surface 
spring  two  stout  ribs,  which  unite  with  a  Fig.  5. 


8  POPULAR  PHYSIOLOGY. 

single  piece  of  bone  in  front.  This  is  our  typical  vertebra ;  and  as  I 
go  on,  the  reader  will  observe  how  simple  and  beautiful  the  arrange- 
ment of  the  skeleton  appears,  when  we,  as  it  were,  unfold  its  mysteries 
by  the  application  of  this  key.  We  begin  with  the  chest.  This  bony 
cage,  which  during  life  contains  the  heart  and  lungs,  is  really  nothing 
more  than  twelve  of  these  vertebrae  (d,  fig.  6)  piled  up  one  on  the  other, 
the  upper  ones  having  smaller  ribs  than  the  lower,  and  a  few  of  the  last 
having  their  ribs  not  united  in  front.  The  breast  bone  is  only  the  sum  of 
the  front  bones  of  the  vertebras,  which  have  become  soldered  together. 
How  is  this  a  protective  case  ?  The  triangular  arches,  locked  one  in 
the  other,  form  a  long  canal,  which  contains  the  "  spinal 
marrow,"  a  great  nervous  organ,  and  the  ribs  cover  in 
the  delicate  apparatus  of  the  lungs  and  heart,  which, 
if  exposed  to  external  pressure,  would  soon  cease  to 
carry  on  the  vital  processes.  Between  the  chest  and  hips 
we  have  a  column  of  bone  which  supports  the  former, 
and  rests  upon  another  that  we  shall  speak  of  presently. 
This  column  is  composed  of  five  vertebrae  (/),  whicli  arc 
like  our  model,  with  this  difference  :  their  ribs  and  front 
pieces  are  not  bony,  but  of  a  sinewy,  or  flexible  descrip- 
tion. It  would  be  singularly  unfortunate  were  there 
osseous  ribs  in  this  situation,  for  within  lie  the  stomach 
and  intestines ;  and  oh !  what  would  become  of  the 
Aldermanic  race  were  not  this  region  capable  of  disten- 
sion? Nature,  foreseeing  the  future  advancement  of 
the  gastronomic  art,  has  wisely  provided  against  the 
horrible  contingencies  that  might  arise,  if  a  man's  belly 
were  boxed  in  bones.  Beneath  the  pillar  of  vertebras 
I  have  been  just  describing  lies  another,  which,  however, 
has  its  component  parts  so  fused  together  as  to  be 
inseparable.  This  is  firmfy  wedged  between  the  bones  of  the  hip,  and 
is  the  foundation-stone  of  the  whole  spine.  It  is  called  the  sacrum  (s), 
from  the  notion  which  prevailed  formerly,  that  when  at  the  last  day 
all  the  other  bones  had  crumbled  into  dust,  from  it  the  whole  skeleton 
would  be  reconstructed.  Its  ribs  do  not  complete  the  circle  and 
unite  in  front,  but  are  merely  flattened  pieces,  which  connect  it  to  the 
hips  on  each  side.  The  tail,  or  coccyx  (ex),  as  it  is  termed,  from  being 
supposed  to  resemble  the  bill  of  a  cuckoo,  consists  of  four  little  bones 
placed  end  to  end,  and  continuous  with  the  sacrum ;  in  these  9ur 
model  vertebra  has  been  deprived  of  all  its  appendages,  and  nothing 
but  the  central  body  remains.  I  trust  the  reader  will  not  be  sur- 
prised to  learn  that  he  does  possess  a  tail,  for  that  such  he  has  is 
unquestionable ;  and  were  the  bones  which  form  it  drawn  out  a  little, 
we  should  be  then  provided  with  a  decided  but  I  fear  not  very  digni- 
fied caudal  extremity. 

We  started  at  the  chest,  because  that  locality  furnished  the 
best  illustration  of  our  model ;  we  must  now  proceed  to  deal 
with  the  other  regions.  The  neck  is  formed  by  a  row  of  seven 
vertebrae  (c),  resting  upon  those  of  the  chest.  These  have  their 
central  parts  ;  and  back  arches  containing  the  spinal  marrow ;  but 


Fig.  6. 


ARMS  AND  LEGS.  \) 

where  are  their  ribs  ?  They  do  not  come  round  to  the  front  ?  No  ! 
The  reader  will  be  astonished  to  learn  that  they  twist  backwards  on 
each  side,  and  in  this  way  make  a  series  of  little  bony  rings,  through 
which  run  certain  blood-vessels  to  the  brain.  Ay,  but  why  are  they 
not  arranged  as  they  are  in  the  chest  ?  Simply  because,  in  the  first 
place,  they  have  no  organs  near  them  which  require  great  protection  ; 
and  in  the  second,  let  me  ask  you,  Sir,  Madame,  or  Miss,  how  you 
could  possibly  give  your  friend  that  familiar  nod,  or  indulge  in  that 
quiet  confabulation,  or  get  down  that  dear  blue  pill  or  bolus,  if  there 
was  a  great  bony  collar  round  your  throat,  just  like  that  of  a  croco- 
dile ?  The  last  portion  of  our  protective  framework  is  the  skull. 
This,  complex  though  it  seems  at  first  sight,  may  be  reduced  to  three 
vertebra,  one  of  whose  ribs  is  represented  by  the  lower  jaw.  It  is 
fixed  on  the  top  of  the  back-bone,  of  which  it  is  an  expansion ;  and 
just  as  the  back -bone  contains  the  spinal  marrow,  so  does  the  skull 
contain  the  brain,  which  is  the  continuation  of  that  marrow.  It  would 
be  too  perplexing  to  the  reader  to  wade  through  this  subject  further, 
so  I  shall  now  say  a  few  words  about — 

The  Locomotive  Skeleton. — This  is  constituted  of  two  pairs  of  ex- 
tremities, somewhat  similar  in  form,  and  attached  to  the  protective 
framework  by  intervening  bony  girdles,  which,  though  apparently 
very  different  from  each  other,"  have  very  many  characters  in 
common. 

These  girdles  may  be  distinguished  by  the  terms  "  upper "  and 
"lower"— the  first  sustaining  the  arms,  the  second  the  thighs  and 
legs.  Each  is  composed  of  six  pieces,  or  three  pairs  ;  those  in  the 
upper  one  are,  the  shoulder-blade,  the  collar-bone,  and  the  coracoid* 
ot  each  side ;  and  in  the  lower  one,  the  hip  bones.  To  the  reader 
there  may  be  some  slight  difficulty  in  grasping  this  idea,  for  the  hips 
are,  in  the  adult,  represented  by  two  solid  buttresses  of  osseous 
material,  but  in  the  infant,  the  hip  on  each  side  is  composed  of  three 
distinct  portions — the  ilium,  ischium,  and  pubes,  which  in  after  life 
become  so  blended  together  as  to  leave  the  mark  of  union  obscure. 
We  have,  then,  three  pairs  of  bones  in  each  girdle,  which  represent 
each  other,  as  shown  in  the  subjacent  table : — 

UPPER  GIRDLE.  LOWER  GIRDLE. 


2  Blade  bones 
2  Collar  ditto 
2  Coracoids 


2  Ilia. 
2  Pubes. 
2  Ischia. 


In  the  upper  belt  the  three  components  unite  to  form  a  socket  for 
the  head  of  the  arm,  and  similarly  in  the  lower  one  the  point  of  union 
of  the  three  bones  is  situate  in  the  hollow  excavated  for  the  ball  of  the 
thigh.  The  two  ilia  may  be  looked  on  as  the  blade-bones  of  the  hips. 
The  shoulder  blade  moves  freely  on  the  back  of  the  ribs,  because  it 
is  necessary  that  the  arm  should  possess  great  freedom  of  motion. 
Now,  the  blade-bone  of  the  hip  is  attached  to  the  stunted  ribs  of  the 

*  So  called  from  being  supposed  to  have  the  form  of  a  raven's  (Korax) 
beak. 


10  POPULAR  PHYSIOLOGY. 

lower  vertebrae;  but  in  order  to  give  firm  support  to  the  entire  trunk, 
it  is  strongly  soldered  to  these  ribs,  and  does  not  glide  easily  over 
them,  as  in  the  shoulder.  The  extremities  are  made  up  of  similar  parts, 
arranged  on  the  same  plan.  There  are  two  pairs,  one  for  each  girdle ; 
the  upper  being  for  the  purpose  of  prehension  or  grasping,  the  lower 
for  locomotion.  The  prehensile  extremities  consist  each  of  a  long  shaft, 
working  by  a  ball-and-socket  joint  in  the  shoulder,  two  smaller  bones 
lying-  side  by  side,  and  hinging  upon  the  end  of  the  first,  two  rows  of 
small  squarish  bones  at  the  ends  of  these,  and  finally  the  hand.  The 
long  shaft  is  the  arm,  the  two  following  make  the  fore-arm,  and  the 
double  row  of  small  bones  constitutes  the  wrist  (vide  fig.  3).  In  the 
thigh,  leg,  and  foot,  the  conformation  of  parts  is  much  the  same,  but 
can  be  more  readily  conceived  by  contrasting  the  two  limbs,  and  by 
glancing  at  the  table  beneath : — 

LOCOMOTIVE  EXTREMITY.  PREHENSILE  EXTREMITY. 

Thigh     . .     . .   1  bone.  Arm        . .     . .    1  bone. 

Leg        . .     . .   2  bones.  Fore-arm        . .  2  bones. 

Heel      . .     . .   7*  bones.  Wrist      . .     . .   8  bones. 

Foot.  Hand. 

It  is  to  be  regretted,  that  space  will  not  permit  me  to  enter  fully 
into  the  wonderful  evidences  of  design  exhibited  by  the  various 
bones,  joints,  and  mechanical  contrivances  of  the  skeleton;  but  it 
would  be  quite  foreign  to  the  scope  of  a  writer  on  pure  physiology  to 
enter  into  more  details :  and  indeed  I  feel  that  I  have  already  tres- 
passed too  much  upon  tne  province  of  the  human  anatomist  in  entering 
so  far  into  the  subject. 

Up  to  this  we  have  been  considering  the  hard  parts  of  man ;  we 
must  now  take  a  peep  at  his  softer  ones.  These  embrace  two  groups — 
that  which  helps  to  carry  on  the  processes  common  to  animals  and 
plants,  the  vegetal;  and  that  peculiar  to  the  former,  the  animal 
group.  The  vegetal  division  embraces  the  heart,  lungs,  liver,  kidneys, 
intestines,  stomach,  &c. ;  the  animal  portion  includes  the  brain,  spinal 
marrow,  nerves,  muscles  (flesh),  and  tendons.  The  first  set  is  divided 
between  the  chest  and  belly,  but  in  both  positions  is  guarded  by  the 
ribs,  and  has  the  osseous  column  of  the  back-bone  behind  it.  The  chest 
and  belly  are  not  continuous,  inasmuch  as  a  great  oblique  mass  of  flesh, 
or  muscle  (diaphragm),  which  is  adherent  all  round  to  the  last  ribs, 
shuts  off  one  from  the  other,  partition  fashion.  Above  this  septum,  and 
within  the  bony  ribs,  lie  the  lungs,  having  the  heart  and  great  blood- 
vessels between  them ;  and  below  are  placed  the  liver,  stomach, 
kidneys,  bladder,  sweetbread,  and  intestines,  as  shown  in  the  adjoining 
cut  (fig.  7).  The  organs  of  the  so-called  animal  class  are  of  two  kinds 
— the  nervous  and  muscular.  The  nervous  system,  of  which  a  more 
detailed  account  shall  appear  elsewhere,  comprises  the  brain,  spinal 
marrow,  and  nerves  ;  the  two  first  are  enclosed  in  the  canal  formed 

*  Though  there  are  but  seven  bones  in  the  adult  heel,  yet  the  true  heel- 
bone  is  the  result  of  the  fusion  of  two  distinct  portions. 


THE   SOFT  PARTS. 


11 


by  the  vertebra,  which,  piled  up  one  above  the  other,  compose  the 
back-bone ;  and,  by  expanding  at  the  top  of  this  latter,  the  skull  also. 
The  muscles  clothe  the  entire  skeleton,  and  are  either  long  bands 
or  triangular  pieces  of  flesh,  arising  from  one  set  of  bones  and  inserted 
into  another,  whose  actions  we  shall  study  in  a  future  chapter. 
Finally,  the  integument,  or  skin,  is  a  mpre  or  less  dense  covering 
which  sheathes  the  entire  body  and  contains  a  vast  series  of  glands, 
which  form  the  perspiration  fluid. 


Spittle  Gland 
Windpipe    ^  -  -v. 


Spittle  Gland. 


Great  Intestine 
Small  Intestine 


°f  *lie  Chest  and  Belly  of  an  Ape«  showing  the  positions  of 

The 


12  POPULAR  PHYSIOLOGY. 


CHAPTER    III. 

Life — Opinions  as  to  the  Nature  of  Life — Advantage  of  not  defining  Life- 
Discoveries  of  Berthelot — Force — Correlation  of  the  Physical  Forces 
— Views  of  Grove— Concealment  of  Light  and  Heat  "by  Plants — 
Organization — Action  of  Platinum  on  Oxygen  and  Hydrogen,  and  of 
decaying  Meat  on  Sugar— Development  of  the  Lower  Plants — Inde- 
structibility of  Force  and  of  Matter — Death — Importance  of  knowing 
when  Death  is  present — Case  of  Drowning — Meaning  of  the  word 
Physiology — School  of  Materialists  and  School  of  Principle-ists— Sir 
E.  B.  Lytton's  Novel,  "A  Strange  Story." 

WHAT  is  life  ?  This  is  a  question  which  has  puzzled  almost  every 
physiologist  from  the  time  of  Aristotle  downwards;  and  which,  it  seems, 
we  are  not  likely  to  get  a  reply  to  for  some  considerable  period. 
There  is  hardly  a  work  on  physiology  extant  but  what  contains  some 
peculiar  proposition  relative  to  the  nature  of  life ;  and  I  think  we 
may  pretty  safely  conclude,  that  by  far  the  greater  number  of  the 
definitions  which  have  been  framed,  are  little  more  than  general 
expressions  of  what  we  understand  by  the  term,  without  any  attempt 
at  an  explanation  of  the  phenomena  it  involves.  Thus,  we  find  one 
set  of  savans  asserting  that  life  is  the  operation  of  a  vital  principle ; 
another,  that  it  is  due  to  a  special  organic  force ;  a  third,  that  it  is  the 
total  of  the  processes  which  resist  death  ;  and  a  fourth,  that  it  is  the 
sum  of  the  actions  performed  by  a  living  body.  In  fact,  life  is  life ; 
and  there's  an  end  to  it.  The  reader  must  not  expect  us  to  display 
our  ignorance.  We  are  philosophers.  ^The  public  will  be  content 
with  some  long-winded  explanation,  which  it  repeats  parrot-like,  or 
as  a  child  does  its  prayers.  Hence  it  follows  that  so  many  false 
statements  have  been  made.  There  never  has  been  an  induction  on 
strictly  logical  principles  concerning  the  nature  of  life  ;  for  the  simple 
reason  that  we  are  as  yet  not  sufficiently  acquainted  with  the  facts. 
All  knowledge  consists  in  facts  and  ideas ;  and  in  a  science  such  as 
physiology,  no  advance  can  be  made  so  long  as  men  form  the  ideas 
first,  and  then  distort  the  facts  to  suit  their  darling  speculations.  ^  It 
is  much  wiser  to  confess  our  general  ignorance  of  the  matter,  just 
stating  what  we  do  know,  and  leaving  it  to  the  future  investigations 
of  others  to  complete  our  labours.  If  we  were  to  commence  the 
erection  of  a  building,  and  discovered  after  a  while  our  utter  inability 
to  complete  it,  would  it  not  be  better  to  wait  patiently  (just  preserv- 
ing the  fruit  of  our  work  from  the  influence  of  the  weather),  till  an 
architect  arrived,  who  was  sufficiently  skilled  to  terminate  the  opera- 
tions we  had  undertaken,  than  to  continue  the  process  ourselves, 
and  so  not  only  construct  something  which  must  tumble  to  pieces  in 
the  course  of  a  few  months,  but  to  display  our  own  bungling  ingenuity 
to  all  who  had  the  capacity  to  perceive  it.  Let  it  here  be  admitted, 
then,  that  we  do  not  yet  know  what  life  is  ;  but,  furthermore,  let  it 
also  be  said  that  we  are  making  rapid  strides  towards  an  elucidation 


CORRELATION  OF  FORCES.  13 

of  the  mystery,  and  that  it  is  not  impossible  that,  before  the  end  of 
the  present  century,  we  may  possess  very  lucid  ideas  regarding  the 
true  cause  of  the  different  vital  phenomena.  Physiology  is  in  a  great 
measure  dependent  for  its  advancement  upon  the  progress  of  the 
other  natural  sciences,  and  of  organic  chemistry  ;  and  as  long  as  such 
extraordinary  discoveries  as  those  of  Berthelot  continue  to  be  re- 
corded,* so  long  will  the  science  of  life  remain  oscillating. 

One  of  the  most  distinguished  investigators  in  the  physical  science 
world— Mr.  Grove— has  for  seme  years  been  enunciating  the  doc- 
trine, that  but  one  force  exists  in  the  inanimate  world ;  that  is  to  say, 
that  light,  heat,  electricity,  magnetism,  gravity,  &c.,  are  not  distinct 
forces,  but  one  and  the  same,  which,  as  it  were,  shows  itself  in  dif- 
ferent ways,  under  different  circumstances,  as  it  passes  from  our  ob- 
servation, but  which  is  never  lost.  Nothing  can  be  more  sublime 
than  this  generalization,  or  more  calculated  to  ennoble  our  sentiments 
of  the  Creator.  Matter  is  indestructible,  so  also  is  force ;  and  the 
two,  mutually  co-operating,  originate  all  those  phenomena  of  which 
our  senses,  carrying  to  the  mind  ideas,  enable  us  to  unravel  and  un- 
derstand. Let  us  endeavour,  in  a  rough  way,  to  illustrate  this  grand 
law  of  Grove's.  A  seed  is  placed  in  the  earth,  it  germinates,  and 
after  successive  years  of  exposure  to  the  influence  of  this  one  force 
(as  heat  and  light),  it  draws  mineral  matters  from  the  earth,  and 
woody  material  from  the  atmosphere— in  fine,  becomes  a  lordly  tree ; 
owing  to  a  series  of  geological  changes  it  is  converted  into  coal,  this 
coal  is  thrown  into  the  grate  of  a  locomotive,  it  is  then  resolved  into 
the  separate  elements  of  which  it  was  originally  composed,  and  light 
and  heat  are  evolved;  the  latter  operating  upon  the  water  in  the 
boiler  causes  it  to  expand,  producing  steam ;  steam  operates  upon 
the  machinery,  giving  rise  to  mechanical  force ;  this  urges  forward 
the  engine,  overcoming  the  resistances  of  the  atmosphere  and  friction, 
and  so  the  original  force  glides  out  of  our  sight,  to  return  again  in 
some  one  or  other  of  the  foregoing  conditions.  The  schematic 
arrangement  beneath  may  assist  in  explaining  what  has  been  described 
above  :— 


Germ 


Mineral  matter, )  (  Mineral  matter, 

water,  carbonic  >=  tree  =  coal  <  water,  carbonic 
acid,  ammonia  )  (  acid  &  ammonia 


when 
burnt. 


Coal     j  S  '  een  C°n     LigM  and  heat. 


This  explanation  must  not  be  regarded  as  strictly  accurate  in  detail  ; 
but  only  such  as  may  serve  to  give  the  reader  a  notion  of  the  actual 

*  Berthelot  has  within  the  past  twelve  months  discovered  a  process,  by 
means  of  which  he  has  united  two  gases,  oxygen  and  hydrogen,  in  such  a 
progressive  manner  as  to  produce  alcohol  (spirit  of  wine). 


14  POPULAR  PHYSIOLOGY. 

"correlation  of  the  physical  forces."  Many  of  the  functions  per- 
formed by  the  human  organs  can  be  explained  by  reference  to  the 
ordinary  laws  of  chemistry  and  physics  ;  out  there  are  certain  other 
processes  which  are  as  yet  inexplicable,  coming  under  the  denomi- 
nation of  organization.  Thus,  the  reader  may  see  that  our  real 
knowledge  of  life  is  that  of  about  a  moiety  of  the  entire  phenomena, 
and  for  those  operations  of  the  living  body  which  we  are  not  yet  in  ia 
position  to  understand,  we  have  coined  the  expression  organization. 
The  following  history  of  the  early  life  of  one  of  the  lowest  forms  of 
vegetables  will  illustrate  this  more  fully. 

In  its  adult  state  this  _  plant  is  a  small  vesicle,  or  bladder,  very 
transparent,  filled  with  fluid  matter,  and  small  granular  particles  ;  in 
dying  it  bursts,  and  sets  free  the  molecules,  each  of  which  commences 
converting  itself  into  a  structure  the  same  as  the  parent,  and  this  act 
is  thus  performed  Being  surrounded  by  an  atmosphere  containing 
watery  vapour,  carbonic  acid  gas,  and  ammonia,  it  so  affects  these 
latter,  as  to  cause  a  breaking  up  of  some,  and  a  union  of  others,  till 
it  develops  a  material  similar  to  the  white  of  egg  ;  when  a  sufficient 
quantity  of  this  substance  has  been  collected  around  the  granule,  the 
outer  layer  undergoes  peculiar  changes,  by  virtue  of  which  it  assumes 
the  features  of  a  membrane  enclosing  the  entire  mass ;  next,  the 
gramde  in  the  centre  draws  into  it  some  of  the  matter  which  it  has 
developed,  and  causing  it  to  partake  of  its  own  characters,  then 
splits  up  into  several  portions,  after  which  the  membrane  bursts,  and 
so  on,  as  before. 

Carbonic  Acid. 


Carbon  Oxygen    .    .     .    Set  free. 


Hydrogen 

Water. 


^  Nitrogen.  Hydrogen.  ^ 

Ammonia. 

Fig.  8. 

The  first  of  these  changes,  which  I  have  thus  endeavoured  to 
delineate  diagramatically,  is  most  probably  a  purely  chemical  one ; 
for  we  know  that  platinum,  in  a  state  of  very  fine  powder,  will  cause 
the  union  of  oxygen  and  hydrogen  gases  and  the  formation  of  water ; 


LIFE  AND  DEATH.  15 

and  a  piece  of  animal  flesh  thrown  into  a  solution  of  sugar  will  break 
that  compound  up  into  its  constituent  parts.  The  second  and  third 
come  under  the  head  pf  organization,  that  is  to  say,  we  believe  they 
are  performed  in  obedience  to  the  laws  of  organization,  or,  in  other 
words,  we  know  nothing  whatever  about  them.  It  might  be,  that  the 
conversion  of  the  outer  portion  of  the  jelly-like  substance  into  mem- 
brane is  partly  due  to  chemical  change,  and  in  some  measure  also  to 
a  change  of  temperature,  whilst  the  division  and  growth  of  the  con- 
tained particles  may  be  a  process  akin  to  that  of  crystallization ;  but 
be  they  what  they  may,  we  r.re  not  yet  sufficiently  acquainted  with 
these  organization-changes  to  lay  down  any  law  respecting  them. 

If  the  reader  can  comprehend  the  remarks  1  have  now  made,  he 
will  have  as  clear  a  notion  of  the  nature  of  life  as  the  first  physiologist 
in  the  world;  our  information  may  be  tersely  written  as  follows. 
"Life  is  the  mutual  co-operation  of  the  physical  forces  (or /bra?)  and 
organized  matter."  Life  is  a  condition  of  perpetual  change,  and  the 
greater  the  vital  activity,  the  greater  will  be  the  extent  of  this 
change.  Every  action  of  a  living  being,  everv  movement,  every 
thought  is  accompanied  by  the  waste  of  a  definite  amount  of 
structure,  just  as  tne  larger  the  surface  of  the  wick  within  a  lamp, 
the  brighter  and  more  luminous  the  flame,  but  proportionally  the  more 
extensive  the  exhaustion  of  the  combustible  pabulum,  or  supply. 
During  life  certain  materials  robbed  from  the  inorganic  world  (having 
been  retained,  pro  tempore,  within  the  body  in  disguise)  pass  from 
their  living  prison,  and  are  restored  to  the  source  from  whence  they 
were  primarily  derived.  How  sublime  is  this  scheme,  and  how 
significant  of  the  truth  of  that  maxim  which  says,  "All  nature  moves 
in  circles."  "  Dust  thou  art,  and  unto  dust  thou  shalt  return." 
Assuredly  this  is  but  too  true ;  and  so  is  the  remark  of  Hamlet : — 

Imperial  Caesar  dead,  and  turned  to  clay, 
Might  stop  a  hole  to  keep  the  winds  away. 

Death,  the  antithesis  of  life,  we  cannot  fully  interpret  till  we 
increase  our  knowledge  of  the  latter.  If  we  suppose  life  to  result 
from  the  exhibition  of  "  force  "  operating  on  organized  bodies,  and 
then  conceive  that  this  force,  not  supplied  with  the  conditions  favour- 
able to  the  production  of  vital  action,  has  degenerated  into  chemical 
decomposition  of  the  organism,  we  shall  have  some  idea  of  death. 
It  is  frequently  stated  in  text-books  on  physiology  that  death  is  of 
two  kinds :  first,  that  in  which  all  the  functions  of  the  body  cease, 
but  where  the  latter  does  not  become  putrid  ;  secondly,  when  putre- 
scence makes  its  appearance.  The  former  description  of  death  has 
the  term  somatic  (soma,  the  body)  applied  to  it,  whilst  the  other  is 
called  molecular.  It  seems  unjust  to  call  that  state  of  the  body  death, 
where  vitality  has  ceased  only  so  far  as  we  are  capable  of  observing  it, 
because,  though  unperceived  by  us,  life  may  linger  still,  the  last  faint 
flicker  of  the  lamp  of  existence  may  still  be  there,  the  flame  of  life  may 
not  yet  be  extinguished,  as  shown  in  many  cases  of  recovery  from  the 
effects  of  drowning.  One  instance  is  remarkable  as  bearing  especially 
upon  this  question.  A  man  was  removed  from  the  water  in  which  he  had 


16  POPULAR  PHYSIOLOGY. 

been  immersed,  and  was  found,  to  all  appearance,  perfectly  dead.  The 
usual  appliances  were  tried  unsuccessfully ;  he  seemed  completely 
asphyxiated ;  the  skin  was  cold  and  clammy,  the  heart  had  ceased  to 
beat,  there  was  no  breathing, — in  fact,  there  seemed  not  the  slightest 
reason  to  hope  for  restoration  to  life.  Some  good  friends,  less 
impatient  and  impetuous  than  others,  determined  that  they  would 
leave  no  means  untried  to  resuscitate  him,  and  with  this  object  caused 
him  to  be  placed  in  a  warm  bed,  placed  hot  jars  to  the  feet  and 
stomach,  and  continued  to  apply  friction  in  the  most  praiseworthy 
manner  for  nineteen  hours;  at  the  end  of  which  period,  to  their 
intense  delight  and  wonder,  the  symptoms  of  returning  C9nsciousness 
made  themselves  manifest.  In  this  case  there  was  every  indication  of 
death  having  taken  place,  and  the  modern  physiologist  would  inform 
you  that  "  somatic  death"  held  his  sway.  For  my  own  part,  I  think 
the  use  of  these  designations  is  more  calculated  to  confuse  than  any- 
thing else.  As  we  are  yet  most  ignorant  of  the  character  of  death, 
we  ought  to  employ  the  expression  in  its  correct  acceptation,  and 
only  consider  a  man  dead  when  the  first  stage  of  decomposition  has 
made  its  appearance.  Having  so  far  treated  of  the  distinction  between 
lite  and  death  in  the  most  cursory  and  outlinear  manner  possible,  it 
behoves  us  to  inquire  into  the  true  limits  of  the  subject  we  have 
taken  in  hand — physiology.  This  is  the  science  of  life ;  that  branch 
of  study  connected  with  the  phenomena  of  living  things,  or  which 
teaches  us  how  the  apparatus  of  animals  and  vegetables  work. 
The  name  is  derived  from  two  Greek  words — phusis,  which  means 
the  supreme  animating  principle,  and  logos,  which  signifies  a  dis- 
course. 

Dear  me !  what  a  strange  and  complicated  piece  of  machinery  \ 
How  does  it  act?  Who  has  not  at  one  period  or  other  of  his 
or  her  life  made  these  remarks  ?  I  shall  fancy  them  addressed  to 
myself,  and  shall  in  the  following  pages  undertake  the  task  of  con- 
ducting the  reader  from  the  basement  to  the  upper  story  of  the 
human  factory,  and  of  describing  in  as  brief  a  way  as  is  consistent 
with  clearness  the  various  processes  by  which  the  crude  material,  in 
the  shape  of  food,  is  eventually  transformed  into  the  delicate  and 
complex  fabrics  of  the  human  body. 

Before  terminating  this  chapter  let  me  commend  to  the  reader  who 
would  learn  in  the  most  pleasing  mode  the  difference  between  the  two 
schools  of  physiologists— materialists  and  principle-ists— the  recent 
production  of  Sir  E.  B.  Lytton,  entitled  "  A  Strange  Story."  No- 
thing could  be  more  lucidly,  attractively,  or  correctly  stated  than  the 
cases  of  the  two  sides  by  this  eminent  writer ;  and  although  I  cannot 
concur  in  the  opinions  *  of  the  distinguished  novelist  upon  certain 
questions,  still,  I  confess  to  having  been  amply  repaid  for  the  time 
spent  in  the  study  (it  must  not  be  read  lightly)  of  this  most  interesting 
and  philosophic  work. 


*  If  indeed  an  author  be  responsible  for  the  opinions  expressed  by  any 
of  the  characters  introduced  into  his  works. 


TISSUES.  17 


CHAPTER    IV. 

Tissues — What  is  a  Tissue  ? — Controversy  among  Physiologists— A  Cell — 
The  Cell  Theory — Development— How  a  Sinew  is  formed. 


THERE  is  still  another  branch  of  our  subject  which,  though  some- 
what introductory,  we  have  not  vet  touched  on.  I  fear  some  may  think 
these  details  too  dry  and  technical,  but  it  must  be  remembered  that 
all  beginnings  are  more  or  less  uninteresting^  as  the  fair  reader,  who 
has  invariably  skipped  over  the  preface  to  Scott's  stories,  may  per- 
chance be  aware.  "I  come  t9  speak"  on  the  subject  of  man's 
tissues.  You  will  perhaps  inquire,  What  is  a  tissue  ?  It  is  one  of 
the  materials  of  which  the  frame  is  composed,  and  which  seems  to 
result  from  the  weaving  together  of  certain  lesser  parts  called  fibres 
or  cells.  Every  portion  of  the  human  tabernacle  is  tissue  of  some 
kind  or  other.  It  builds  up  muscle,  and  is  termed  muscular  tissue, 
or  nerve,  hence  nervous  tissue,  or  bone,  from  which  bony  tissue, 
is  employed  to  form  an  organ  which  extracts  substances  from 
the  blood — a  gland — and  is  then  termed  glandular  tissue,  and  so  on. 
Now,  as  to  the  minute  structure  which  these  different  fabrics  present 
when  examined  with  the  highest  power  of  the  microscope,  an  awful 
battle  is  taking  place  among  physiologists  at  the  present  day.  The 
conflict  is  not  confined  to  Britain,  but  rages  over  the  Continent  also, 
and  the  first  men  in  this  department  of  science  have  put  forward 
their  opinions.  But  this  is  not  all ;  another  section  is  at  war  con- 
cerning the  infant  features  of  the  tissues  and  regarding  their  gene- 
alogy ;  and  as  the  questions  referred  to  excite  considerable  interest 
among  scientific  men,  a  short  resume  of  what  has  been  proved  on 
each  side  may  not  be  unacceptable. 

It  is  necessary  in  the  first  place  to  state  that  the  controversy  turns 
on  this  point :  Is  the  body  C9mposed  of  little  vesicles  or  cells?  And 
here  I  must  premise  my  outline  by  giving  the  following  definition  of 
a  cell:— it  is  a  minute  bladder,  closed  all  round ;  its  outside  resembles 
gelatine,  that  is  to  say  it  is  perfectly  transparent,  and  has  no  (appar- 
ent) structure ;  inside  there  is  liquid,  and  floating  in  this  a  small 
granular  rough  mass  called  a  nucleus ;  withal,  it  is  so  diminutive  as  to 
be  seen  only  by  the  help  of  a  good  microscope.  A  German  anatomist 
wrote  a  book  some  years  ago  to  prove  that  every  tissue  in  the  human 
body  was  made  up  of  these  cells,  and,  I  suppose,  satisfied  himself  of 
the  truth  of  his  hypothesis ;  it  was  a  very  nice  idea,  and  "  took  "  ex- 
ceedingly well  for  some  years,  having  been  supported  by  many  of  the 
philosophers  in  this  country  and  Germany ;  but  "  every  dog  has  his 
day,"  and  so  with  the  poor  "  cell  theory,'"  for  after  a  short  reign  a 
most  Socratic  Brutus  slaughtered  it  unmercifully,  but  justly;  if  you 
would  ask  me  the  name  of  this  tyrant  slayer,  I  should  not  tell  you : 
he  is  9116  whose  claims  to  distinction  have  not  yet  received  the 
recognition  they  merit  so  well ;  he  is  an  Englishman,  and  a  naturalist 

c 


18  POPULAR,  PHYSIOLOGY. 

and  one  who  will  hereafter  be  regarded,  in  comparative  anatomy,  as 
the  Bacon  of  the  nineteenth  century.^  Verbum  sapientibus,  he  bore 
"a  banner  with  this  strange  device''5  —  Development.  Ay,  but 
what  is  development  ?  Ah  me  !  What  a  nuisance  it  is  to  have  these 
horri'd  long  words  turning  up  so  often.  Lend  us  a  hand  then,  or  we 
shall  stumble.  I  cannot  define  development  more  tersely  than  it  has 
been  done  by  a  recent  writer,  who  says,  "it  is  the  process  by  which  a 
being  or  organism  is  brought  from  what  it  was  to  what  it  is."  To 
return,  then.  This  gentleman  said,  If  you  want  to  know  what  a  struc- 
ture is,  first  learn  what  it  teas ;  and  pursuing  this  view  he  worked 
indefatigably  at  the  development  of  portions  of  the  body,  and  showed, 
/think,  conclusively,  that  at  all  events  all  tissues  are  neither  cells  in 
the  adult  nor  in  their  infant  state ;  so  the  German  theory,  as  uni- 
versally applicable,  we  may  regard  as  being  now  (to  use  a  slang  expres- 
sion) absquatulated. 

As  regards  the  earliest  condition  of  all  tissues,  there  is  yet  much 
to  be  learned.  A  most  interesting  theory  has  been  put  forward  within 
the  present  year,  but  inasmuch  as  it  may  be  regarded  as  sub  judice, 
I  shall  not  enter  into  it  here.    The  doctrine  I  have  been  accustomed 
to  teach,  is  one  that  was  promulgated  some  years  since,  and  which  I 
regret  to  find  has  not  been  treated  with  the 
A  B          consideration  it  deserves.  In  a  few  words  it 

is  this.  All  structures  in  the  body,  no 
matter  what ;  be  they  nerve,  muscle,  skin, 
or  bone,  start  in  the  same  way,  and  from  the 
same  point,  on  their  journey  to  what-they- 
will-be ;  one  may  take  this  line,  another 
that ;  one  may  travel  by  express,  another 
parliamentary ;  each  may  arrive  at  a  dif- 
ferent terminus,  but  all  commence  their 
adventures  under  the  same  form.  Let  us, 
for  example,  take  a  bit  of  a  sinew,  and 
watch  its  progress  :  first  (A,  fig.  9)  it  con- 
sists of  a  jelly-like  transparent  substance, 
through  which  (like  raisins  in  plum  pudding) 
are  scattered  numbers  of  little  granular 
Fig.  9.  particles,  imperceptible  to  the  naked  eye. 

After  a  while  we  find  the  jelly  substance 

expanding  in  such  a  way  as  to  have  a  small  cavity  round  each 
granule  (B).  These  cavities  increase  in  size  and  run  into  each  other, 
so  that  we  have  now  the  sinew  composed  of  solid  bands  of  jelly,  and 
hollow  bands  containing  granules  as  in  C. 

Next,  we  find  the  walls  of  the  hollow  bands  closing  in  on  each 
other,  and  converting  themselves  into  fibres,  whilst  the  jelly  hardens 
and  assumes  the  appearance  of  a  number  of  flattened  threads  (D), 
and  the  perfect  sinew  is  formed. 

This  description  must  suffice  for  all,  and  if  it  is  stated  so  that 
the  reader  can  apprehend  the  various  stages  of  the  development,  a 
great  step  will  have  been  made.  The  cavity  which  the  intervening 
soft  material  leaves  round  the  granule  is  what  the  German  anatomist 


TISSUES— FOOD.  19 

mistook  for  a  cell ;  of  course,  in  the  ordinary  sense  it  is  a  cell,  but  if 
employed  in  this  acceptation  it  would  not  be  of  any  use  in  carrying 
out  his  views,  and  in  the  strictly  physiological  meaning  it  is  no  cell 
at  all.* 

The  account  above  given  will  answer  in  a  rough  way  for  all  tissues ; 
but  if  it  be  asked,  Why  does  one  become  flesh  and  another  bone  ? 
I  answer.  We  cannot  tell.  Why  does  one  mineral  assume  one  par- 
ticular geometrical  form,  and  another  another  ?  Did  the  narrow  limits 
of  this  volume  allow  me,  I  should  here  enter  minutely  into  the  de- 
scription of  the  microscopic  characters  of  bone,  flesh,  nerve,  and  such 
like  ;  but  it  would  occupy  too  much  space,  and  would,  I  dare  believe,  be 
tedious  to  the  general  reader  ;  therefore,  I  shall  now  pass  on  to  the 
more  truly  physiological  branch  of  the  subject,  merely  observing  that 
for  the  minuter  features  of  the  tissues,  the  following  books  may  be 
consulted  with  advantage  :  Carpenter  on  /'The  Microscope  and  its 
Revelations,"  Todd  and  Bowman's  "  Physiological  Anatomy,"  Quain 
and  Sharpey's  "  Elements  of  Anatomy,"  and  Kolliker's  "  Manual  of 
Human  Histology." 


CHAPTER    Y. 

Food — Classification  of  Aliments — Alcohol — Opinions  of  Teetotallers — 
Effect  of  Spirits  upon  the  Body — Combustion  and  Decomposition  of 
Alcohol— Duchek's  Experiences — Composition  of  Dublin  Porter — 
Value  of  German  Beer — Views  of  Liebig — Importance  of  Sugar  as  a 
form  of  Food — Blubber  and  the  Esquimaux — Nutritious  Properties  of 
Flesh — Cheese — Materials  necessary  for  the  formation  of  Bones — Use 
of  Salt — Constituents  of  Milk — Tissue-repairing  Power  of  Tea  and 
Coffee — Gelatine  and  Soups — Are  Broths  and  Jellies  nutritious? — 
What  is  a  Poison — Popular  Idea  of  the  Action  of  Mercury — Strychnine 
the  Food  of  a  Bird — Bread  made  of  Flour  and  Clay — No  animal  can 
live  upon  one,  form  of  Food — Experiments  of  Magendie — Death  of 
Dr.  Stark— Cause  of  Hunger— Thirst  and  Satiety— Is  the  habit  of 
smoking  Tobacco  injurious?  —  Common  Sense  versus  False  Philo- 
sophy. 

IN  that  self-repairing  machine,  the  animal  body,  the  raw  material 
which  is  woven  into  the  several  tissues  is  termed  Food.  One  would 
think  it  could  not  be  so  very  difficult  to  know  what  food  is,  but  it  is 
not  so  easy  a  matter  after  all,  and  food  has  for  some  time  past  been 
a  bone  of  contention  to  physiologists. 

We  may  say  that  food  is  a  substance  or  combination  of  substances 
which  supplies  to  the  body  some  material  or  materials  of  which  it  is 
composed.  It  is  of  the  following  kinds  :— 

*  Except  possibly  to  the  misguided  Deutschlander. 
c  2 


20  POPULAR  PHYSIOLOGY. 

( Water  (1). 
Liquid  \  Alcohol  (2). 

(  Beer,  wine,  &c.  (3). 


FOOD 


Not  mineral 


( Eats,  starch,  sugar,  gums  (4). 


Solidm .  I  (  Flesh,  eggs,  gluten,  &c.  (5). 

Mineral  ..     I  Common  and  other  salts  (6). 

Heretofore,  it  has  been  customary  to  classify  the  various  forms  of 
food  under  two  heads, — those  of  nutritious,  and  heat-producing.  This 
method,  however,  was  not  based  upon  a  perfect  knowledge  of  the 

Sarts  which  each  class  of  materials  playe.d  in  the  body,  and  hence 
shall  not  adopt  it.  Teetotalers  have  long  objected  to  the  view 
which  holds  that  alcohol  is  food,  asserting  that  it  is  a  poison,  and 
shocking  the  minds  of  all  rational  men  by  advocating  the  intro- 
duction of  a  "  Maine  liquor  law."  Media  tutissimus  ibis.  We  need 
not  run  into  either  extreme ;  we  may  surely  "  send  round  the  bowl " 
without  reducing  ourselves  to  the  condition  of  beasts ;  and  if  a  portion 
of  the  population  will  be  brutes,  the  rest  should  not  be  deprived  of  rea- 
sonable indulgence  in  alcoholic  drinks.  By  parity  of  reasoning,  because 
a  certain  percentage  of  the  British  people  annually  select  carving- 
knives  as  a  medium  of  conveyance  to  another  world,  the  remainder 
should  at  once  be  obliged  to  employ  "  chop-sticks"  for  the  future.  No, 
no,  dear  reader,  be  assured  that  teetotalism,  as  also  phrenology,  mes- 
merism, electro-biology,  homoeopathy,  and  such  like,  will,  in  the 
course  of  another  century  (when  our  bodily  atoms  are  transformed 
into  cabbage-plants),  be  looked  on  as  a  few  of  the  eccentricities  of 
this  enlightened  age. 

Before  I  attempt  to  show  the  use  of  alcohol,  it  must  be  understoot 
that  the  waste  of  the  body  which  food  repairs  is  not  entirely  withou 
an  end  or  purpose ;  the  refuse  or  effete  matter  is  absolutely  burnei 
out  of  the  system,  and  such  burning  produces  the  heat  which  animal 
could  not  exist  without.  If  some  compound  be  introduced  into  th 
body  which  will  burn  of  itself,  the  tissues  do  not  then  undergo  s 
much  destruction,  because  there  is  no  special  need  of  their  eonsump 
tion;  now,  this  is  exactly  what  takes  place  when  spirits,  whether  IE 
the  shape  of  wine,  whisky,  brandy,  rum,  or  beer,  is  taken  into  th 
stomach,  and  from  this  we  learn  that,  though  not  acting  directly,  the 
act  indirectly  as  food.  _  If  the  alcohol  is  burnt  in  the  spirit-lam; 
(which  is  the  series  of  minute  bloodvessels)  of  the  animal  economy,  i 
must  be  altered  in  character,  because  it  must  unite  with  the  oxygei 
of  the  air  which  has  been  carried  from  the  lungs.  The  question  turn. 
on  this  point :  and  as  recent  investigations  of  teetotalist  philosopher 
go  to  prove  that  the  alcahol  passes  unchanged  from  the  skin,  lungs 
and  kidneys,  their  researches  deserve  some  consideration : — 

1st.  Supposing  their  experiments  to  have  been  fairly  and  accuratel 
conducted,  they  only  prove  that  certain  minute  portions  of  the  alcoho 


ALCOHOL  AND  BEER.  21 

passed  out  in  a  pure  form,  and  these  might  be  accounted  for  by  the 
iact,  that  enormously  large  doses  had  been  administered ;  and  they 
have  failed  to  prove  that  all  the  alcohol  was  expelled  unchanged. 

2d.  Supposing  certain  portions  did  pass  out  unaltered,  this  would 
not  prove  that  it  was  not  food,  because  as  certainly  does  water  (which 
is  food,  and  part  of  which  is  decomposed  in  the  body),  pass  out  in  its 
pure  form  also. 

3d.  Duchek  and  many  others  have  found  it  in  the  altered  state  in 
the  different  tissues. 

That  spirits,  in  the  form  of  whisky  or  brandy,  do  maintain  the 
animal  heat,  I  fancy  no  one  who  has  ever  enjoyed  (?)  a  day's  sporting, 
or  spent  a  w^eek  investigating  the  geology  of  a  bleak  mountain  dis- 
trict, can  for  a  moment  deny.  I  myself  have  experienced  the 
delightful  glow  of  warmth  which  steals  over  the  body  after  a  long 
day's  exposure  to  hills  and  hunger,  on  the  application  of  the  lips  to  a 
well-charged  flask  of  cognac;  and  I  fear  I  am  too  much  of  a  sceptic  to 
be  readily  convinced  that  the  pleasing  sensation  was  due  to  the 
irritatiiKj  and  poisonous  effects  of  the  "  eau  de  vie." 

As  bearing  on  the  alcohol  question,  I  must  say  a  few  words  for  our 
beer.  I  have  often  heard  people  decry  beer  as  a  beverage  "  fit  only 
for  besotted  boors ;"  but  when  I  consider  the  enormous  proportion  of 
beer-drinkers  in  the  population  of  Europe,  and  the  composition  of  the 
venerable  John  Barleycorn  himself,  I  feel  sufficiently  philosophic  to 
adopt  the  common-sense  opinion— that  it  is  no  sin  to  DC  a  Malt-ese. 
Porter  and  beer  we  may  class  together,  for  the  effects  of  one  are 
pretty  nearly  the  same  as  those  of  the  other,  and  hence  an  analysis  of 
the  first  will  give  us  a  clue  to  their  common  properties. 

In  1,000  parts,  by  measure,  of  porter  there  are  of — 


Proof  spirit 
Vinegar  . . 
Grape  sugar 
Albumen  . . 
Phosphates 
Common  salt 


89'6 
3'6 
172 
8-272 
0-851 
0'448 


A  glance  at  the  above  table  must  be  sufficient  to  convince  even  the 
most  sceptical  of  the  highly  nutritious  quality  of  this  form  of  food. 
It  is  true  that  Liebig  believes  that  a  man  who  has  been  drinking 
several  pints  of  beer  per  day  does  not  receive  more  nutrition  at  the 
end  of  the  year  than  he  who  has  just  eaten  a  4  Ib.  loaf;  but  any  one 
who  has  travelled  in  Germany  will  admit  the  existence  of  a  very  well 
marked  distinction  between  the  "good  Bairisch  bier"  of  that  country 
and  London  porter.  1  must  say  that  to  my  taste  the  Bairisch  and 
Christiania  beer  drunk  in  Deutschland  seems  more  like  the  washings 
of  an  English  brewery  than  anything  else ;  and  if  the  philos9phic 
Baron  indulged  in  a  twelvemonth's  course  of  these  fluids,  with  a 
view  to  testing  the  truth  of  his  own  researches,  he  certainly  deserves 
well  of  his  country. 

In  fine,  I  may  observe,  as  an  argument  In  support  of  the  use  of 
spirituous  liquids,  that  there  is  hardly  a  nation  on  the  face  of  the 


22  POPULAR  PHYSIOLOGY. 

earth,  no  matter  how  aboriginal,  but  what  possesses  its  own  intoxi- 
cating drink  ;  and  the  Scripture  narrative  of  Noah's  little  peccadilloes 
I  need  hardly  remind  the  reader  of.  Schiller,  in  his  beautiful  poem, 
"The  Eour  Elements,"  thus  describes  the  addition  of  the  various 
constituents  of  the  emblem  of  hospitableness  and  conviviality: — 

Four  elements  joined  in  an  ermilous  strife, 
Build  up  the  world,  %nd  constitute  life. 
First  from  the  citron  the  starry  juice  pour  ; 
Acid  to  life  is  the  innermost  core. 

Now  let  the  sugar  the  bitter  one  meet ; 

And  the  strength  of  the  acid  be  tamed  with  the  sweet ; 

Bright  let  the  water  flow  into  the  bowl ; 

For  water  in  calmness  encircles  the  whole. 

Next  shed  the  drops  of  the  spirit  within ; 

Life  but  its  life  from  the  spirit  can  win. 

Drain  quick,  no  restoring  when  cool  can  it  bring  ; 

The  wave  has  but  virtue  drunk  hot  from  the  spring. 

So  much  for  the  subject  of  alcohol.  Baron  Liebig,  who  may  be 
regarded  as  the  first  chemist  of  this  century,  thinks  that  all  foods, 
such  as  fats,  oils,  starch,  &c.,  are  only  employed  to  maintain  the 
animal  heat,  and  are  usually  burnt  up  in  the  olood-vessels.  We  can 
hardly  doubt  that  combustion  of  these  materials  does  take  place 
(without  absolute  flame) ;  but  I  think  the  great  German  philosopher 
goes  one  step  too  far  when  he  says  that  is  their  only  purpose.  Eat  is 
as  important  a  constituent  of  the  tissues  as  white-of-egg,  or  any 
other  substance ;  and  when  it  is  not  taken  in  some  shape  or  form,  the 
body  becomes  emaciated :  this  we  know  from  two  circumstances ; 
first,  every  portion,  to  the  smallest  microscopic  particle,  of  the  soft 
parts  contains  fat ;  secondly,  when  a  person  is  unable  to  eat  fatty 
materials,  and  that  dread  disease  consumption  has  fastened  itself  upon 
the  lungs,  it  is  only  by  the  use  of  such  medicines  as  will  enable  him 
or  her  to  digest  fats,  that  we  can  ever  hope  for  a  cure.  In  connection 
with  this  idea  of  the  cause  of  consumption,  a  most  remarkable  fact 
has  been  noticed,  viz.,  if  in  a  family  of  ten  children  there  is  one  who 
for  years  has  exhibited  an  aversion  to  fat  and  butter,  it  is  more  than 

Erobable,  nay,  almost  certain,  that  should  any  member  of  that  family 
e,  in  after  years,  attacked  by  consumption,  it  will  be  the  one  who 
has  shown  .the  peculiar  distaste  referred  to.  But  bounteous  nature 
has  provided  an  alternative,  which,  if  adopted,  often  serves  to 
eradicate  the  germs  of  scrofula.  It  is  this  :  sugar  is  capable  of  being 
converted  into  fat,  and  children,  who  abominate  the  notion  of  fatty  or 
buttery  food,  absolutely  crave  for  sugar;  and  here,  en  passant,  a  word 
to  economical  (?)  mothers.  Never  forbid  your  children  the  use  of 
sugar,  forsooth,  because  Dr.  What-d'ye-call-'em  says  'twill  ruin  their 
teeth,  or  prevent  digestion.  Don't  deny  the  innocent  darlings  the 
pleasure  of  spending  their  little  pocket-money  in  lollipops ;  for  be 
assured  that  in  so  doing  you  are  only  helping  too  abundant  conditions 


FAT  AND  PLESH.  33 

to  sow  the  germs  of  what  I  believe  every  family  possesses  in  some 
measure— scrofula.  Let  us,  then,  lift  our  hats  to  the  pastrycooks, 
for,  mayhap,  they  are  labouring,  unwittingly,  to  save  us  from  more 
ill-health  and  unhappiness  than  we  imagine. 

It  must  not  be  thought  that  sugar  will  suffice  for  the  wants  of  the 
animal  economy ;  but  that  it  is  converted  into  fat  we  know  from  this 
fact ;  bees  when  fed  upon  it  will  produce  wax,  and  wax  contains 
much  oleaginous  or  fatty  matter.  However,  experiments  made  in 
Trance  to  determine  how  long  bees  could  continue  to  exist  on  sugar 
alone,  show  that,  after  a  lapse  of  time,  the  insects  cease  to  work,  and 
if  not  given  honey  they  dp  not  survive.  That  fat  and  oils  maintain 
the  temperature  of  the  body  cannot  be  doubted,  although  it  is  equally 
true  that  all  the  tissues,  in  giving  rise  to  "sewage,"  or  effete  mate- 
rials, do  the  same.  It  is  said  of  the  Esquimaux,  that  one  of  them 
can  devour  as  much  as  201b.  of  blubber,  with  the  greatest  gusto,  in 
a  single  day.  Every  one  knows  of  the  proverbial  predilection  of  the 
Russians  for  grease.  I  have  heard  the  master  of  a  Hamburgh  whaler 
state,  that  one  occasion,  having  sent  one  of  his  crew  (a  Russian)  down 
to  the  hold  to  see  after  some  cases  of  tallow  candles,  he  observed  the 
fellow,  on  his  return  to  the  deck,  spit  from  his  mouth  a  whitish  cottony 
mass,  which  on  examination  proved  to  be  the  wicks  of  some  two  or 
three  candles.  Moreover,  if  I  mistake  not,  some  one  has  asserted 
that,  on  the  approach  of  cold  weather,  the  London  butter  retailers 
increase  the  price  per  pound,  knowing  that  a  greater  demand  will  be 
made  (as  it  were  instinctively)  for  this  kind  of  food. 

Flesh  or  meat,  which  is  the  next  variety  of  food,  is  considered  to 
be  the  most  nutritious  ;  but  as  nutrition  itself  is  a  very  relative  term, 
it  is  difficult  to  admit  the  truth  of  this  assertion.  That  the  sub- 
stances of  which  it  is  composed  are  capable  of  building  up  most  of 
the  animal  structures  is  true  enough ;  but  on  these  alone  man  cannot 
subsist.  When  flesh  or  muscle  has  been  exposed  to  water  for  a  con- 
siderable time,  it  is  converted  into  a  liquid  resembling,  in  every  par- 
ticular, white-of-egg ;  indeed,  it  must  be  reduced  to  this  condition 
before  it  is  of  service  in  repairing  the  bodily  waste ;  and  from  this  there 
seems  very  good  reason  for  the  view  of  its  high  nutritive  properties.  To 
show  this  it  is  only  necessary  to  refer  to  the  egg,  and  the  young  fowl. 
AYhat  is  an  egg  ?  It  is  an  oval  mass  of  organic  and  mineral  matter,  con- 
sisting of  the  white  (albumen),  fat,  sulphur,  and  salts.  Now,  as  out 
of  these  the  perfect  fowl,  with  flesh,  blood,  bone,  sinew,  skin,  brain,  and 
feathers  is  constructed,  we  have  here  adequate  evidence  to  prove  the 
great  nutritious  qualities  of  the  entire  mass.  Vegetable  food,  some  folk 
would  say,  should  not  be  classed  under  the  head  of  "flesh;"  this  is, 
however,  an  error,  and  the  old  division  of  aliments  into  fish,  flesh,  and 
fowl  is  also  no  longer  tenable.  Besides  the  albumen  which  flesh  is 
formed  of,  there  is  in  the  body  another  substance  with  which  every 
OUR  is  familiar,  under  the  name  of  cheese.  It  is  found  in  milk3  and 
differs  from  albumen  in  this,  that  if  you  add  some  vinegar  to  a  liquid 
containing  cheese  in  solution,  it  falls  to  the  bottom  of  the  vessel  as 
curds ;  in  fact,  this  is  the  theory  of  cheese-making.  Vegetables  con- 
tain two  substances  identical  with  albumen  and  cheese,  and  which  may 


24-  POPULAR  PHYSIOLOGY. 

be  extracted  by  peculiar  methods.  The  first  is  found  in  all  kinds  of 
corn-grains ;  the  second  in  seeds  of  the  pea  and  bean  kind.  This 
is  known  even  to  the  Chinese,  who  manufacture  from  beans  a  sort  of 
cheese  very  much  resembling  many  of  our  British  kinds. 

As  "  there  is  never  smoke  without  fire/'  so  do  we  see  there  is  some 
truth  in  the  view  of  vegetarianists.  Many  would  laugh  if  told  that  bone- 
dust  was  food ;  but  let  them  reflect  for  a  moment  what  is  bone-dust. 
The  powdered  skeleton  of  an  animal.  How  did  the  animal  make  the 
skeleton?  By  taking  in  its  food  the  minerals  which  it  required.  In  truth, 
dear  reader,  did  you  not  swallow  bone-dust  at  some  period  of  your  life 
you  would  now  be  in  a  sorry  plight.  Did  you  ever  hear  of  a  disease 
called  "rickets  ?  "  No;  well,  it  is  a  state  of  the  system  when  no 
bone-dust  has  been  made  into  bones ;  and  in  this  disease  one  can 
virtually  put  one's  feet  in  one's  pockets,  for  one  has  no  longer  solid 
thigh  or  leg  bones,  but  flexible,  as  if  they  were  made  of  india-rubber. 
So  you  see  we  must  eat  minerals,  and  the  principal  sorts  we  require  are 
the  following : — 

Common  salt. 

Phosphate  of  lime.     e  • 

Phosphate  of  magnesia. 

Limestone,  or  chalk. 

Carbonate  of  soda  (washing  soda). 

The  first  has  been  employed  as  aliment  from  time  immemorial ;  we 
find  it  mentioned  in  the  Bible  as  having  been  most  extensively  used  by 
the  Jews.  "  If  the  salt  hath  lost  its  savour,  wherewith  shall  it  be 
salted  ? "  Eastern  travellers  also  describe  it  as  being  a  mark  of 
respect  on  the  part  of  potentates  to  present  each  other  with  salt. 
There  is  no  portion  of  body  in  which  it  may  not  be  found.  Even 
among  the  lower  animals  the  desire  for  salt  is  often  very  powerfully 
shown ;  for  instance,  in  some  of  the  wild  districts  of  America  there 
are  portions  of  the  soil  strongly  impregnated  with  common  salt,  and 
it  is  so  well  known  that  in  certain  seasons  these  localities  are 
thronged  by  hundreds  of  buffaloes  and  other  wild  cattle,  seeking  this 
compound,  that  they  have  been  called  the  "  Buffalo  licks." 

The  other  mineral  ingredients  are  abundant  in  vegetable  food, 
as  corn,  bread,  potatoes,  cauliflowers,  &c.  &c.  The  young  of 
Mammalia*  are  dependent  for  subsistence  upon  the  milk  of  the 
mother,  and  as  this  liquid  maintains  life  and  forwards  the  growth  of 
the  being  for  some  time,  an  inquiry  into  its  composition  and  pro- 
perties may  aid  us  in  forming  a  general  idea  of  the  kinds  of  food 
which  such  an  animal  requires.  Milk  is  composed  of — 

Water, 
Butter, 
Cheese, 
Sugar, 

Common  salt, 

Phosphates  and  carbonates, 

*  Animals  which  have  teats,  and  feed  their  infant  offspring  upon  milk. 
From  the  Latin  mamma,  a  teat. 


TEA,   COFFEE,   AND  SOUP.  25 

which  are  the  very  articles  of  diet  that  every  one,  high  or  low,  con- 
sumes from  day  to  day  ;  for  though  albumen  (white-of-egg)  be  not 
here  present,  we  may  look  on  cheese  as  only  a  very  slightly  modified 
form  of  this  principle,  and  one  which  is  converted  into  a  substance 
similar  to  albumen,  prior  to  its  absorption  into  the  blood  through  the 
vessels  of  the  stomach.  . 

We  have  now  travelled  over  most  of  the  food  ground ;  but  since 
there  are  two  alimentary  compounds  in  general  use  which  come 
under  no  distinct  class,  and  to  which  we  have  not  yet  alluded,  1  shall 
treat  of  them  shortly.  Tea  and  coffee— are  they  nutritious  ?  I  think 
the  answer  must  be  in  the  affirmative,  at  any  rate  in  the  way  in 
which  we  use  them.  But  whether  tea  and  coffee  are  intrinsically 
nutritive  compounds  is  a  question.  When  they  have  been  submitted 
to  chemical  analysis  two  peculiar  crystalline  salts  have  been  obtained, 
which  are  respectively  called  Theme  and  Caffeine.  These  contain  a 
very  large  percentage  of  nitrogen,  and  therefore  would  be  thought 
by  the  Liebig  school  of  chemists  to  be  of  great  tissue-repairing  value. 
I  very  much  doubt  they  are  ever  concerned  in  the  reconstruction 
of  the  soft  parts.  It  appears  to  me  that  their  chief  use  is  as  stimu- 
lants of  an  agreeable  description,  and  which  are  somewhat  preserva- 
tive ;  that  is  to  say,  have  the  power,  to  prevent  waste  ot  the  bodily 
structures.  This  View  is  substantiated  by  the  loss  of  general 
appetite  experienced  by  that  most  respectable  class  of  society— the 
aged  tea-drinking  females. 

It  will  not  be  out  of  place  here  to  say  two  or  three  words  on  the 
subject  of  soups  and  gelatine.  An  endless  amount  of  misconception 
exists  in  reference  to  these  materials.  It  is  stated  that  soups  are 
innutritious  because  they  contain  gelatine,  which  is  also  useless  as  a 
nutritive  substance.  I  do  not  know  of  any  physiologist  who  has  so 
philosophically  and  interestingly  treated  on  this  question  as  Mr.  G.  H. 
Lewes.*  I  cannot  concur  in  all  his  opinions,  but  1  fully  agree  with 
him  regarding  the  illogical  manner  in  which  the  conclusions  of  those 
who  would  exclude  gelatine  from  the  class  of  nutritious  food  are 
drawn.  Great  excitement  was  produced  some  years  since  in  Paris 
by  the  announcement  that  gelatine  was  highly  nutritious,  and  could 
easily  be  extracted  from  all  sorts  of  bones  by  a  process  of  continued 
boiling.  In  all  the  public  charities  boilers  and  extensive  apparatus 
for  the  manufacture  of  gelatine  were  erected,  and  as  the  poor  flocked 
in  great  numbers  and  were  supplied^with  the  soup  extracted  in  this 
manner,  apparently  ample  opportunities  were  afforded  of  testing  the 
truth  of  the  doctrine.  But  the  product  proved  anything  but 
nutritious,  and  gave  rise  to  diarrhoea  and  other  unpleasant  symptoms 
of  imperfect  digestion.  Mr.  Lewes  wittily  but  truly  observes : — 
"  The  savans  heard  this  with  great  equanimity.  They  were  not  the 
men  to  give  up  a  theory  at  the  bidding  of  vulgar  experience. 
Diarrhoea  was  doubtless  distressing,  but  science  was  not  implicated 
in  that."  And  so  the  affair  went  on  from  bad  to  worse,  till 

*  Physiology  of  Common  Life,  in  2  vols.  By  G.  H.  Lewes.  Blackwood 
&Co.  '1859. 


26  POPULAR  PHYSIOLOGY. 

the  Academy  having  been  assured  of  the  innutritive  qualities  of 
gelatine,  decided  against  it.  In  1833  two  distinguished  French- 
men brought  the  matter  a  second  time  forward,  it  was  again 
defeated  by  the  Academy,  and  so  it  rests.  Gelatine  is  therefore  con- 
sidered by  most  modern  physiologists  as  useless  food.  Is  there  of 
my  readers  any  one  who  has  been  an  invalid,  and  during  con- 
valescence has  been  confined  to  a  gelatinous  diet  ?  If  so,  I  would 
ask  him,  has  he  not  felt  substantial  proof  of  the  nutritive  power  of  the 
delicious  broths  and  jellies  with  which  his  kind  nurses  have  provided 
him  ?  Does  he  reply  in  the  negative  ?  Then  I  take  the  question 
myself,  and  say,  /  most  assuredly  have  been  rebuilt  bodily  by  a  diet 
consisting  of  broths  and  jellies^  Besides,  the  strongest  argument 
against  gelatine  is,  that  it  alone  is  incapable  of  sustaining  life.  We 
shall  see  presently  how  this  also  applies  to  every  article  of  food 
taken  separately,  and,  therefore,  by  the  same  line  of  argument,  we 
should  arrive  at  the  painful  conclusion  that  there  was  no  food  in 
the  universe. 

Chemists  tell  us  that  after  gelatine  has  been  taken  into  the  system 
a  large  quantity  of  urea  is  found  in  the  urine,  and  that  this  shows 
the  want  of  nutritious  power  in  the  gelatine ;  but  by  what  abtruse 
mode  of  reasoning  they  have  come  to  this  result  we  are  not  informed. 
That  gelatine  is  nutritious  I  think  we  have  fair  reason  to  suppose, 
while  there  is  not  a  tittle  of  real  evidence  on  the  other  side.  We 
may  therefore  take  it  for  granted  as  extremely  probable  that  soups, 
broths,  jellies,  and  their  kin,  are  of  considerable  value  as  articles 
of  diet. 

The  questions  we  have  up  to  this  time  been  discussing  relate  to 
food,  and  lead  us  by  an  easy  gradation  to  the  question,  What  is 
poison  ?  I  know  nothing  more  difficult  to  define  than  this  expres- 
sion, and  though  hosts  of  wordy  and  technical  significations  are  to 
be  found  in  works  on  forensic  medicine,  I  believe  I  am  not  out- 
stepping truth  in  asserting  that  none  are  faultless.  Let  us  say  a 
poison  is  some  substance,  which,  when  allowed  to  act  of  itself,  either 
within  or  upon  the  body,  tends  to  produce  death.  Thus  arsenic  is  a 
poison  if  applied  to  the  skin,  and  still  more  so  if  taken  int9  the 
stomach.  Pounded  glass  will  produce  death,  if  swallowed,  by  giving 
rise  to  inflammation  of  the  intestinal  canal ;  and,  strange  to  say,  pure 
mercury,  even  if  so  much  as  a  pound's  weight  of  it  be  taken,  will 
give  rise  to  no  dangerous  effects  at  all.  _  There  are  queer  notions 
afloat  among  the  public  about  the  retention  of.  mercury  within  the 
system.  Be  it  known  then,  that  three  weeks  after  even  the  largest 
dose  of  blue  pill  has  been  taken,  not  a  particle  of  it  can  be  found 
within  the  body.  To  prove  this,  men  who  have  been  poisoned  by 
mercury,  but  who  lingered  on  for  this  period,  have  been  regularly 
boiled  down,  and  carefully  examined,  yet  never  has  the  faintest  trace 
of  this  metal  been  discovered.  Even  common  table  salt  is  a  poison,  and 
cases  are  on  record  of  death  from  the  swallowing  of  this  substance. 
Again,  a  salt  which  one  man  can  resist  the  action  of  proves  fatal  to 
another,  thus_  showing  the  truth  of  the  adage  "  One  man's  meat  is 
another's  poison."  Strychnine,  whose  properties  everyone  in 


CLAY  AND   FOOD.  27 

England  is  too  well  acquainted  with,  is  said  to  be  poisonous  to  every 
animal  except  one,  and  this  is  a  species  of  bird  of  the  genus  Horn- 
bill,  which  is  said  to  live  upon  the  nux  vomica  nuts,  from  which  this 
"  deadly  poison"  is  derived. 

Apropos  of  food,  it  is  a  curious  fact  that  unless  the  stomach  be 
nearly  filled,  the  sensation  of  hunger  remains,  but  if  with  the  aliment 
there  be  mixed  mineral  matter  which  is  entirely  indigestible,  the 
feeling  of  starvation  vanishes.  Thus  Humboldt  says  of  the  people  of 
Oronoco  that  they  often  mixed  earth  with  their  food,  and  when  asked 
the  reason  for  this,  replied  that  they  did  it  because  thev  knew  the 
stomach  should  be  filled.  In  the  famine  which  occurred  in  1832  on 
the  borders  of  Lapland,  the  people  of  Degerna  formed  a  kind  of 
bread  by  baking  together  flour,  the  bark  of  trees,  and  a  peculiar  clay, 
which,  when  analysed,  was  found  to  contain  nineteen  different  forms 
of  Diatomacese  *  in  the  fossil  condition.  What  a  little  treasure  for 
some  of  our  enthusiastic  microscopists  the  bellies  of  these  poor 
Laplanders  would  have  been. 

No  animal  can  cpntinue  to  exist  if  provided  with  but  one  and  the  same 
article  of  diet.  This  has  been  proved  by  feeding  dogs  upon  sugar  alone, 
the  result  of  which  has  been  emaciation,  loss  of  appetite  and  strength, 
listlessness,  the  appearance  of  ulcers  in  the  eyes,  and  death  after 
from  thirty-one  to  thirty-six  days.  Magendie  fed  a  dog  on  white 
bread  and  water,  and  found  that  he  survived  but  fifty  days.  Rabbits, 
guinea  pigs,  donkeys,  fowls,  and  dogs  have  been  fed  upon  one  only  of 
the  following  sorts  of  food :  —  wheat,  oats,  barley,  cabbage,  rice, 
carrots,  hard  eggs,  cheese ;  and  death  has  invariably  supervened  in  a 
longer  or  shorter  period.  We  often  talk  in  this  country  of  keeping 
prisoners  on  bread  and  water  diet,  but  few  are  aware  in  how  short  a 
time  this  would  produce  death.  In  Denmark  it  is  so  well  known, 
however,  that  a  diet  of  bread  and  water  for  four  weeks  is  considered 
to  be  synonymous  with  capital  punishment. 

Dr.  Stark  (who,  being  desirous  of  ascertaining  the  effects  of 
restriction  to  a  diet  of  one  kind,  began  a  series  of  experiments  upon 
himself)  discovered,  when  too  late,  the  truth  of  the  above  statement, 
and  perished  in  his  honest  endeavours  to  advance  science.  Oh,  ye 
self-experimenting  physiologists  of  the  nineteenth  century,  let  this  be 
a  dreadful  warning  to  you  !  Beware  of  unintentionally  immolating 
yourselves  at  the  shrine  of  biology  .f 

Having  waded  through  so  much  on  the  varieties  and  actions  of 
food,  the  reader  may  very  naturally  inquire  what  is  the  cause  of 
hunger.  And  here  I  am  at  fault,  for  I  know  not  what  it  is  myself; 
and  furthermore,  I  am  quite  certain  that  those  writers  who  give  such 
diffuse  explanations  of  the  mattter,  are  themselves  as  completely 

*  So  called  from  two  Greek  words,  meaning  to  cut  through  ;  it  being 
the  character  of  these  lowly  and  flinty  plants  to  split  up  into  segments  of 
various  shapes. 

f  The  science  of  life  ;  from  two  Greek  words,  bios',  life,  and  logos,  a 
discourse.  Unhappily,  the  progress  of  charlatanism  in  this  country  has 
created  an  impression  in  the  public  mind  that  the  above  word  has  some 
connection  with  mesmerism. 


28  POPULAR  PHYSIOLOGY. 

ignorant.  All  we  can  say  at  present  is,  that  hunger  is  a  peculiar 
sensation  conveyed  to  the  mind  by  the  nerves  of  the  stomach,  and 
caused,  possibly,  by  the  swollen  state  of  the  vessels  of  this  organ, 
owing  to  the  absence  of  food.  But  this  is  really  little  more  than  the 
reader  is  aware  of  already,  and  he  must  "  take  the  will  for  the  deed." 
Better  to  tell  the  naked  truth,  than  to  lie  in  using  long  and  obscure 
sentences  to  conceal  our  ignorance. 

We  are  in  the  same  condition  of  difficulty  in  regard  to  the  terms 
thirst  and  satiety.  No  precise  or  satisfactory  account  of  the  pro- 
duction of  these  sensations  has  as  yet  been  given.  Several  experi- 
ments have  been  undertaken  to  discover  the  length  of  time  for  which 
animals  can  support  starvation,  but  the  results  have  been  practically 
useless.  We  are  justified,  however,  from  the  records  of  shipwrecked 
mariners  and  forlorn  adventurers,  in  arriving  at  the  conclusion  that 
a  man  suffering  hunger  and  thirst  cannot  live  above  a  week.  If 
deprived  of  food  alone t  he  can  exist  for  a  still  longer  period,  and  if 
he  be  insane,  he  may  continue  to  live  for  an  extraordinary  length  of 
time  (?).  This  general  law  we  may  look  on  as  established.  Warm- 
blooded animals  (mammals  and  birds)  tolerate  starvation  and  thirst 
for  a  much  shorter  duration  of  time  than  those  whose  temperature  is- 
lower,  as  fishes,  amphibia  (Frogs,  &c.),  and  reptiles. 

Ere  I  conclude  this  chapter  let  me  offer  a  few  remarks  on  the 
much  debated  question— Is  tobacco  a  poison?  In  the  CornUll 
Magazine  for  November,  1862,  a  most  valuable  article  appeared  on 
this  subject.  The  writer's  signature  is  not  attached  to  it,  but  evi- 
dently the  author  is  one  highly  competent  to  handle  the  question, 
and  I  conceive  he  has  handled  it  in  a  masterly  manner.  Turn  then, 
dear  reader,  to  the  periodical  alluded  to,  and  fancy,  if  you  like,  that 
I  am  nodding  acquiescence  in  the  statements  therein  contained,  as 
you  scan  or  study  them  according  to  pleasure.  Tobacco,  whether  in 
the  form  of  cigar  or  not,  contains  a  peculiar  principle  of  a  narcotic 
power,  which  is  called,  after  the  plant  itself,*  nicotine.  In  addition 
to  this,  when  burnt  (as  in  smoking),  an  oily  compound  is  formed, 
which  is  poisonous.  These  two  materials  are  not  necessarily 
absorbed  to  an  injurious  extent  by  the  tissues  of  the  body.  There- 
fore, moderate  smoking  is  not,  as  some  would  have  it,  a  most  per- 
nicious habit.  We  are  told  it  expends  the  saliva ;  be  it  so,  what  of 
that  ?  Oh,  my  dear  sir,  it  is  one  of  the  most  important  fluids 
employed  in  digestion.  Qucere — Is  not  the  office  of  the  saliva  a 
purely  mechanical  one,  softening  the  food  to  render  chewing  facile, 
and  oiling,  as  it  were,  the  gullet,  so  that  the  mass  may  slip  easily 
into  the  stomach?  Modern  research  tends  to  shew  the  truth  of  this. 
But,  sir,  tobacco  stimulates  the  nervous  system.  I  say, _ granted; 
and  a  very  delightful  stimulant  it  is ;  whilst,  my  sage  physiologist,  I 
am  to  suppose  that  tea,  coffee,  wine,  beer,  spirits,  pleasure,  are  not 

*  The  tobacco  plant  belongs  to  the  same  natural  order  as  the  potato, 
henbane,  and  bitter-sweet,  and  is  termed  in  botanical  parlance,  Nicotiana, 
tabacum.  Apart  from  its  general  use,  it  is  of  great  value  as  a  medicine, — 
for  example,  in  cases  of  rupture. 


TOBACCO  SMOKING.  29 

stimulants  also.  Eh  ?  Again,  dear  reader,  let  me  advise  you  never  to 
let  fungus  philosophy  triumph  over  common  sense ;  and  when  your 
pigmy  savant  tells  you  that  men  are  smoking  away  their  brains,  point 
to  Germany,  and  say,  Is  there  no  profound  thinking  there  ?  Is  there 
no  mental  power  in  men  who,  as  Thomas  Carlyle,  Lytton  Bulwer, 
and  Thackeray,  are  known  not  omy  to  indulge,  but  to  encourage 
indulgence  m  that  solace  of  the  stu  ent — the  'fragrant  weed  ? 


CHAPTER    VI. 

Digestion — What  we  require  in  order  to  digest  Food — All  Animals  have 
Stomachs— How  the  Amoeba  eats  and  digests— Gullet,  Intestine,  and 
Teeth  are  Appendages — Glands  employed  in  Digestion — Varieties  of 
Teeth — Structure  of  a  Tooth  —  Mastication — The  Spittle  Glands — 
Structure  of  the  Parotid — Use  of  the  Saliva — Experiments  of  Bernard 
— Discovery  of  Lassaigne — Influence  of  the  Mind  upon  the  Secretion  of 
Saliva — Form  of  the  Stomach — Gla  nds  which  form  the  Gastric  Juice — 
Characters  of  the  latter — Pepsin —  How  Food  is  dissolved— Fat  is  not 
dissolved  in  the  Stomach — Fats  and  Starch  digested  in  the  Small 
Intestine — Nature  and  Office  of  a  Villus — Intestinal  Spittle  Glands — 
Function  of  the  Intestinal  Juice—  Structure  of  the  Liver— Use  of  Bile 
— The  Sweetbread — Nerves  which  supply  the  Guts — Length  of  Intes- 
tine dependent  upon  the  Character  of  Food  required — Movements  of 
the  Stomach — Absorption  of  Food  — Chyle — Form,  Position,  and  Use 
of  Lacteals — Time  required  for  the  Digestion  of  various  forms  of 
Food — Quantity  of  Gland  Juice  formed  in  Twenty-four  Hours — 
Amount  of  Food  required  per  Diem —  Indigestion — Dyspepsia — 
Cleanliness. 

A.LL  of  us  know,  in  a  general  way,  what  is  understood  by  the  word 
digestion;  but  perhaps  if  some  were  asked  what  was  necessary  to 
ensure  digestion,  they,  could  not  give  a  very  satisfactory  reply.  There 
are  three  things  requisite  :  1st,  food ;  of  this  we  have  spoken  already. 
2nd,  some  vessel  or  sac  to  hold  the  food  •  and  3rd,  certain  liquids,  to 
dissolve  and  act  upon  the  latter  so  that  it  may  be  taken  up  into  the 
system  by  the  blood-vessels.  The  second  factor— that  of  a  cavity  to 
contain  the  alimentary  substances  whilst  they  are  being  fitted  for 
absorption — is  the  stomach.  It  is  the  chemical  laboratory  of  the 
body,  without  which,  as  very  well  shown  in  the  Roman's  fable  of 
"  The  Belly  and  the  Members,"  life  could  not  be  carried  on.  Here, 
en  parenthese,  I  may  observe  what  may  surprise  a  few  :  a  stomach,  or 
some  approach  to  it,  is  the  only  character  by  which  the  lowest  plants  and 
animals  can  be  contra-distinguished.  Most  animals  have  a  stomach,  or 
gullet  of  some  kind ;  but  even  those  which  possess  no  such  commo- 
dity extemporize  one  when  they  require  it.  Plants  neither  possess 
nor  extemporize  a  digestive  sac. 

Here  is  one  of  the  most  degraded  of  animal  forms— the  little 
'  Amoeba" — a  creature  to  be  found  in  pools  of  fresh  water  in  the 


30  POPULAR  PHYSIOLOGY. 

summer  time,  but  not  so  easily  discovered  as  some  of  our  natu- 
ralists would  lead  us  to  imagine.  Watch  him  closely  !  He  is  but 
an  irregularly-shaped  mass  of  jelly,  and  very  minute ;  moreover, 
he  is  quite  transparent,  and  is  not  (as  our  quack  advertisements 
have  it)  "  troubled  with  a  liver,"  nor  indeed  with  any  organ  at 
all.  He  is  really,  as  a  lady  once  remarked  to  me  of  a  snail— "all 
squash;"  and  yet,  as  I  said  before,  watch  him!  L9  !  a  minute 
animalcule  Ins  just  brushed  past  him.  Ah,  luckless  animalcule,  not 
past!  for  the  Amoeba  has  thrown  out  a  long  whip-like  string  of  jelly, 
in  which  thou  art  entangled.  Struggles  are  unavailing.  The  relent- 
less monster  has  seized  his  quarry;  and  see  !  already  he  is  throwing 
out  other  arms,  hydra  fashion— now  two,  now  four.  In  a  moment  a 
dozen  hungry  arms  have  closed  around  thee.  Stay !  "  What  will 
he  do  with  it?"  Art  thou  to  be  kept  "in  durance  vile,"  hapless 
iufusorian  ?  'Tis  true  thy  cruel  tyrant  hath  got  no  Bastile  in  which 
to  entomb  thee ;  a  far  worse  fate  is  being  prepared.  The  Amoeba  is 
gradually  pushing  his  prey  into  the  substance  of  his  body.  This  has 
subsequently  closed  over  it ;  and  what  do  we  behold  ?  A  transparent 
sphere  enclosing  the  unfortunate  animalcule,  who  is  now  subserving 
the  comfort  of  the  oppressor  by  undergoing  rapid  digestion.  After 
some  time,  when  all  the  nutritious  materials  have  been  abstracted, 
the  remnants  are  Quite  unconcernedly  forced  out  through  some  portion 
of  the  gelatinous  film. 

Fancy  a  little  girl  making  her  first  dumpling,  by  placing  a  piece 
of  apple  and  sugar  upon  a  layer  of  dough,  and  then  tucking  these 
in  so  as  to  form  a  roundish  ball  of  paste,  and  you  will  understand 
very  clearly  the  nonchalance  exhibited  by  our  Amoeba  friend  in 
getting  through  his  meal.  A  stomach,  then,  is  the  simplest  form  of 
digestive  cavity,  and  the  most  essential ;  all  the  other  organs  of 
the  food  system  are  but  superadded.  Thus,  as  we  advance  in  the 
animal  scale,  we  find  the  stomach  placed  in  the  lower  part  of  the 
body.  Therefore  it  is  necessary  that  there  be  a  channel  through  which 
the  food  may  reach  it ;  this,  then,  is  called  a  gullet,  and  its  outer 
opening  the  mouth.  Next  there  must  be  provided  a  canal,  by  which 
the  indigestible  debris  are  carried  away ;  this  is  the  intestine.  Again, 
the  food  of  some  animals  is  of  a  dense  character,  and  must  be  firmly 
divided  before  entering  the  stomach.  To  overcome  this  difficulty 
teeth  are  presented ;  and  so  on,  till  we  find  in  man  the  machinery 
existing  in  its  most  perfect  and  complex  form.  In  the  human  diges- 
tive apparatus  we  have,  in  addi- 
tion to  the  above  components, 
certain  glands.  Glands  are  organs 
composed  of  the  different  tissues 
arranged  in  a  special  manner, 
whose  office  it  is  to  separate,  or 
form  from  the  blood,  fluids  which 
are  some  of  them  of  value,  others 
effete.  The  principal  glandular 
Fig.  iOA.-Skuii  of  the  Boar,  showing  structures  are  those  of  the  mouth, 
^he  three  classes  of  teeth.  which  secrete  the  spittle,  and  are 


STRUCTURE  OF  TEETH.  31 

called  salivary ;  the  liver  and  sweetbread,  which  pour  their  secre- 
tions int9  the  top  of  the  intestines ;  the  sacules,  xvhich  form  the 
gastric  juice,  and  glands  called  after  B  runner,  which  are  found  in  the 
smaller  gut.  The  teeth  of  an  adult  are  thirty-two  in  number— sixteen 
in  each  jaw,  and  are  of  three  kinds — incisor  or  gnawing,  canine  or  chop- 
ping, and  molar  or  grinding  (fig.  H)B).  These  varieties  characterize  dis- 


Large  Molar. 


Small  Molar.    Canine.   Incisive. 


Fig.  1  OB  .—Human  Teeth. 


tinct  orders  of  Mammalia.  The  incisors  are  found  in  animals  of  a 
gnawing  propensity,  as  rats,  rabbits,  beavers,  &c:,  which  are  termed 
Rodents.  The  second  form  of  teeth  is  especially  indicative  of  a  flesh- 
eating  habit,  being  found  most  perfectly  developed 
in  carnivorous  beasts,  as  the  clog  (canis),  whence 
the  name  canine.  The  molars  point  to  an  herbi- 
vorous diet,  and  are  the  principal  teeth  in  such 
grass-eating  creatures  as  sheep,  cows,  and  goats. 
To  the  reflective  mind,  the  mixture  of  these  classes 
of  dental  organs  in  man  is  very  significant,  for  it 
shows  that  the  "lords  of  the  creation"  were  not 
intended  to  subsist  entirely  upon  either  animal  or 
vegetable  diet ;  and  it  is  one  of  the  strongest  argu- 
ments against  vegetarianisms.  A  tooth  is  composed 
of  three  structures,  differing  in  hardness  (fig.  11). 
The  outer— a  very  thin  layer,  and  the  most  dense 
animal  substance  known — is  named  enamel ;  it  forms 
the  crown  of  the  tooth,  and  is  to  it  what  the  steel 
edge  is  to  the  iron  weapon.  Next  comes  the  great 
bulk  of  the  tooth— a  structure  similar  to  ivory,  and 
called  dentine.  It  is  hollow  within,  having  a  cavity 
that,  in  the  living  tooth,  is  filled  with  a  mass  of  fat 
and  nerve.  It  is  prolonged  upward  as  the  fang 
or  fangs  which  fasten  the  tooth  in  the  jaw,  just  as  if 
it  were  a  nail  driven  into  a  board;  and  these  are 
covered  outside  by  the  cement — a  bony  compound,  Fi  11_section 
which  often  is  continuous  with  the  osseous  tissue  of  e0f  Tooth, 
the  jaw,  thus  enhancing  the  agony  which  the  patient 
who  is  having  a  tooth  extracted  must  undergo.  You  may  be  asto- 


32 


POPULAR  PHYSIOLOGY. 


nished  to  learn  that  teeth  and  hair  are  near  relations,  being  "  brought 
up  "  in  the  same  manner,  and  having  a  structure  in  many  ways  similar. 
Indeed  feathers  and  porcupine  quills  come  under  the  same  brother- 
hood also. 

There  being  three  kinds  of  teeth  in  the  jaws  of  man,  it  follows  that  as 
many  distinct  forms  of  motion  must  take  place  during  the  process  of 
mastication.  The  upper  jaw  being  fixed,  it  is  the  lower  upon  which  the 
labour  of  dividing  the  food  chiefly  falls.  This  may  be  moved  back- 
wards or  forwards,  up 
or  down,  and  from 
right  to  left,  by  mus- 
cles for  the  purpose, 
as  shown  in  the  adja- 
cent diagram  (fig.  1-2). 
The  tongue  plays  an 
important  part  in  the 
chewing  of  food ;  by 
reason  of  the  muscles 
of  which  it  is  com- 
posed it  tilts  the  food- 
mass  from  side  to  side, 
so  that  the  large  par- 
ticles are  retained  be- 
neath the  teeth  until 
reduced  to  a  suffici- 
ently fine  condition. 

While  the  process  of 
mastication  is  going 
on,  six  glands  are  ac- 
tively engaged  throw- 
ing out  saliva  into  the 
mouth;  and,  ere  we 
consider  the  use  of  the 
spittle  secretion  and 
its  composition,  we 
must  glance  at  one 
of  the  organs  which 
develope  it.  The  six 
glands  are  so  very 

like  each  other  that  one  description  must  answer  for  all.  Tracing 
one  from  the  mouth,  it  appears  as  a  membranous  canal ;  this  soon 
divides  and  subdivides,  like  the  branches  of  a  tree,  till  there  are  pro- 
duced at  last  exceedingly  minute  tubules.  If,  now,  we  examine  these 
under  the  microscope,  we  see  them  expanding  at  their  extremities 
into  little  bladders  or  sacs,  which  give  the  whole  gland  the  appear- 
ance of  a  cluster  of  grapes  in  miniature  (vide  fig.  13).  Between  these 
sacs  there  are  hosts  of  microscopic  blood-vessels,  both  arteries  and 
veins,  and  finally  all  the  little  nooks  and  crannies  are  filled  up  with  fat. 
The  secretion  is  derived  from  the  blood  circulating  in  the  delicate 
vessels  with  which  the  little  sacs  are  surrounded ;  in  fact,  it  is  but  a 


Fig.  12.— Human  Skull,  with  the  lower  jaw  (a  a) 
depressed ;  g  k,  the  upper  jaw ;  d,  surface  of  the  skull, 
to  which  one  of  the  muscles  (temporal)  is  attached ; 
b,  projection  of  lower  jaw,  in  which  the  same  muscle 
is  inserted.  The  vertical  and  oblique  lines  represent 
the  directions  in  which  the  jaw  can  be  moved. 


THE  SALIVA. 


33 


13. — Intimate  structure  of 
(the  Parotid). 


Spittle  Gland 


Mud  of  percolation  of  the  more  liquid  and  saline  portions  of  this  fluid, 
through  the  coats  of  the  vessels  and  sacs,  into  the  cavities  of  the 
latter,  from  which  it  is  then  conveyed  to  the  mouth  by  the  series 
of  conduits  I  have  described.  If  you  have  borne  in  mind  the  re- 
marks I  have  made  in  another  chapter  on  the  nature  of  osmose,  you 
will  then,  by  the  assist- 
ance of  the  diagram 
(fig.  14),  be  able  readily 
to  comprehend  the  pro- 
cess. 

The  saliva  is  a  some- 
what viscid  liquid,  and 
contains,  besides  water 
and  saline  materials,  a 
quantity  of  a  leavening 
substance  called  ptyaline. 
It  is  usually  alkaline,  but 
in  some  cases  has  been 
found  acid.  Its  uses 
are: — 

1.  To  soften  the  food, 
so  as  to  admit  of  its  being 
more  easily  chewed. 

2.  To  mix  up  air  with 
the  food. 

3.  To  moisten  the  throat  and  gullet,  so  that  the  food  may  glide 
freely  to  the  latter. 

The  third  seems  to  be  its  most  serious  office,  and  the  one  which  is 
most  evident  also.  Who,  for  example,  can  swallow  a  dry  biscuit 
with  ease,  on  first  rising  in  the  morning  ?  In  order  to  ascertain  the 
value  of  saliva,  M.  Bernard  tried  the  following  experiment :— He  cut 
across  the  gullet  of  a  horse  about  mid- 
way between  the  mouth  and  stomach, 
and  then  gave  him  a  pound  of  oats. 
This  the  beast  chewed  and  swallowed 
in  the  course^  of  nine  minutes.  The 
food  was  received  into  a  vessel  placed 
under  the  cut  portion  of  the  gullet,  and 
when  examined  was  found  properly 
masticated  and  saturated  with  saliva. 

Next,  he  caused  the  spittle  to  flow  out 
of  the  mouth  through  an  incision,  and 
administered  another  pound  of  oats. 
On  this  occasion  but  three-quarters  of 
the  food  were  eaten,  and  no  less  than  twenty-five  minutes  were 
expended  in  swallowing  them.  The  mass,  which  as  before  was  received 
into  a  vessel,  was  this  time  found  dry  and  brittle,  and  entirely  devoid 
of  saliva. 

It  appears  that  the  quantity  of  saliva  poured  out  depends  upon 
-the  character  of  the  food ;  if  this  be  hard  and  dry,  there  is  a  large 

D 


Blood-Vessel. 


Saccule. 


Duct. 


Mouth. 


Fig.  14. 


34  POPULAR  PHYSIOLOGY. 

supply  of  spittle,  and  vice  versa.  M.  Lassaigns  proved  this  by  an 
experiment  rather  like  the  one  I  have  just  mentioned.  A  cow  was 
supplied  with  weighed  quantities  of  four  kinds  of  food,  and  an  incision 
having  been  previously  made  in  the  gullet,  these  were,  after  swallow- 
ing, collected  and  re-weighed,  when,  of  course,  the  excess  indicated 
the  amount  of  saliva  employed  in  each  instance.  Thus : — 

Por  100  parts  of  hay,  there  were  absorbed  400  parts  of  saliva. 
„        „        barley  meal,    „        „         186 

oats,     ._,»,,» 
„        „        green  stalks  and  leaves,      49        „        „ 

The  above  researches  afford  a  very  fair  conclusion  as  to  the  func- 
tions which  I  have  attributed  to  the  saliva ;  but  that  it  fulfils  any 
more  useful  office,  I  think  we  are  at  liberty  to  consider  very  question- 
able. 

The  flow  of  spittle  fluid  is  influenced  to  a  great  extent  by  mental 
sensations.  The  appearance  of  delicious  viands  is  often  sufficient  to 
produce  an  increased  quantity  of  the  secretion,  owing  to  the  effect  upon 
the  mind;  of  which  the  proverbial  expression,  "making  the  mouth 
water,"  is  a  very  good  illustration.  Saliva  possesses  the  power  of 
converting  starch  into  sugar.  This  action  takes  place  when  farina- 
ceous food  has  been  retained  in  the  mouth  for  some  time  ;  and  will 
occur  out  of  the  body,  in  a  glass  vessel  for  example.  ^  Physiologists 
have  been  led  from  this  circumstance  to  suppose  that  it  performs  the 
same  part  in  the  stomach ;  but  experiments  have  done  away  with 
this  notion  by  showing  that  the  juices  of  the  stomach  completely 
prevent  the  alteration. 

All  this  time  I  have  been  keeping  you  with  a  bit  in  your  mouth, 
which  may  now  be  swallowed  if  you  please;  but  in  doing  so  you  must 
not  forget  that  the  road  to  the  stomach  is  the  gullet,  and  if  your  food 
parcel  is  sent  "  the  wrong  way/'  the  excise  of  the  wind-pipe  will  very- 
soon  inform  you  of  its  dereliction  of  duty.  Now  comes  the  gullet, 
and  wi.th  it  the  stomach  and  guts,  or  bowels,  as  they  are  more  fre- 
quently designated. 

We  may  look  on  the  entire  alimentary  "line''  as  a  fleshy  tunnel 
or  tube,  blown  out  at  the  stomach  into  a  sac ;  in  the  same  manner 
as  the  London  and  North- Western  Railway,  lying  between  Chester 
and  Euston  Square,  expands  into  the  magnificent  station  in  Bir- 
mingham. The  whole  digestive  canal,  from  mouth  to  opposite 
extreme,  is  made  up  of  three  layers;  a  soft,  sinewy  one  outside,  a 
fleshy  one  in  the  middle,  and  a  beautifully  piled  velvet  lining  within. 

The  stomach  lies  at  the  top  of  the  belly,  and  in  front;  and  has  been 
often  compared  to  a  piper's  bag  in  form  (fig.  15).  It  is  joined  to  the 
gullet  at  its  left  and  upper  border  (a),  and  merges  in  the  small 
intestine  on  its  right  side  (vide  diagram).  It  is  by  the  stomach 
that  the  gastric  (gaster,  the  stomach)  juice  is  secreted,  which  is  of  so 
much  import  in  digestion,  and  which  we  hear  dyspeptic  sufferers 
complain  of  so  often.  How  is  this  stomach  fluid  formed  ?  By 
little  pouches  lying  in  the  velvety  coat,  which  are  generally  shut  up 


GASTEIC  JUICE  AND   GLANDS. 


33 


while  we  are  fasting,  but  as  soon  as  food  is  introduced  throw  out 
their  peculiar  secretion.  The 
whole  inner  surface  of  the 
stomach  is  lined  with  these., 
which  have  the  appearance 
seen  below  when  examined 
microscopically  (figs.  16, 17) . 
The  gastric  juice  is  of  an 
acid  character;  but  whether 
this  sourness  is  due  to  the 
presence  of  vinegar,  spirits  of 
salts,  acid  of  milk,  or  acid 
of  rancid  butter,  is  yet  a  ques- 
tion; indeed,  it  is  quite 
possible  it  may  be  owing  to 
all  of  these.  Its  most  impor- 
tant and  essential  constituent 


is  a  substance  termed  pepsii 
which  acts   upon    all  flesh 


Fig.  15.— Diagram  of  Human  Stomach— 
a  b,  gullet  end ;  h  g,  intestinal  end  ;  c,  left 
border ;  f,  right  border ;  d,  greater  curve; 
e,  lesser  curve. 


.  sin, 

upon  all  fleshy 
foods  as  a  ferment,  reducing 
them  to  the  state  of  white  of 
egg.  It  is  not  improbable  that  this  organic  compound,  pepsin,  may 
act  upon  the  common  salt,  so  as  to  cause  its  decomposition,  and  give 
rise  to  acid.  Thus  •.— 

In  the  N  1. 

stomach     g 
during    '    ' 


Elesh 

Common  salt 

Water.. 


7 


White  of  egg. 


j  Hydrogen 
1  Oxygen 


Soda 


I  cannot  here  go  into  further  details,  and  must  only  hope  that  the 
scheme  above  may  help  to  supply  the  want  of  further  explanation. 
Acids  do  not  dissolve  oils,  therefore,  as  we  might  expect,  fats  un- 
dergo no    solution  in  the    stomach.    Flesh,  and  all  liquids  except 
those  of  a  purely  oleaginous  character,  the  albu- 
minous parts  of  plants  and  bread,  and  saline  materials 
are  dissolved  in  this  locality.    Fat  and  starchy  matters 
pass  into  the  intestines  before  they  assume  the  so- 
luble form.    The  intestines,  whilst  partaking  of  the 
structural  features  of  the  gullet  and  stomach,  have 
many  peculiarities.    All  through  they  are  lined  with 
the  velvet  coating  and  small  pouches,  which  in  the 
stomach  secreted  gastric  juice,  but  which  here  manu-   Oj  giands;  b,  vei- 
iacture  a  viscid  liquid  named  mucus.  This  lubricates   vety  membrane, 
the  food-mass  as  it  travels  along,  and  so  prevents 
injury  to  the  membrane.    The  velvet  surface  is  raised  out  in  little 
conical  projections,  termed?*//*  (fig.  18s),  and  these,  as  we  shall  here- 
after see,  are  the  labourers  employed  to  extract  the  nutritious  ma- 
terials from  the  crude  combinations  of  useful  and  effete.     Each 
villus,  seen  under  the  microscope,  resembles  a  little  teat,  covered  with 

D  2 


36 


POPULAR  PHYSIOLOGY. 


a  velvet  layer  outside,  and  having 
within,  embedded  in  loose  tissue,  a 
delicate  network  of  blood-vessels, 
and  a  small  white  tube  called  a  lac- 
teal, —  of 
which  more 
anon. 

Again, 
buried  in 
the  walls 
ofthelesser 
intestine  is 
a  series  of 
glands  ra- 
ther like 
those  which 
secrete  the 
saliva,  and 
of  the  form 
represented 
below  (fig. 
19).  The 
fluid  crea- 
ted by  these 
organs  is  si- 
milar in  pro- 
perties to 
that  found 
in  the  mouth 
— of  which 
we  have  seen 
enough  al- 
ready. 

In    addi- 

Fig.  17.— Gastric  glands  from  the  tion  to  those  already  mentioned,  there 
stomach  of  a  Pig,  highly  magnified.     are  found  all  through  the  intestines, 

small  oval  white  solid 
bodies,  surrounded  by  a 
circle  of  minute  aper 
tures,  but  of  their  func 
tions  we  really  know 
nothing  yet;  they  are 
collectively  called  the 
glands  of  Peyer.  All 
these  lesser  intestinal 
glands  C9ntribute  to 
form  a  fluid  known  by 
the  name  of  "  intestinal 
juice."  That  it  also 
operates  on  flesh  has 

Fig.  l SB. —Clusters  of  mill,  magnified. 


Fig.  ISA.  —  Network  of 
blood-vessels,  of  a  single 
villus,  greatly  enlarged. 


STRUCTURE  OF  THE   LIVER. 


3? 


been  demonstrated  by  two  German  chemists  in  the  following  manner 
They  made  an  opening  into  the  belly  of  a  dog,  and  drew  out  a  portion 
of  the  intestines,  which  they  then  tied  near  the  stomach,  to  prevent  the 
gastric  juice  coming  down ;  next,  they  opened  into  the  intestine,  and 
placed  in  it  two  or 
three  muslin  bags  con- 
taining weighed  quan- 
tities of  meat,  and 
replacing  it  in  the 
belly,  allowed  the 
animal  to  li ve  for  about 
twelve  hours.  It  was 
then  killed,  and  when 
the  bags  of  flesh  were 
extracted,  and  re- 
weighed,  it  was  found 
that  the  contents  had 
been  altered,  and  the 
weight  diminished. 

Up  to  the  present 
we  have  omitted  con- 
sidering the  two  largest 
organs  in  connection 
with  the  digestive 
system ;  they  are  the 
liver  and  sweetbread. 
The  liver  is  a  very 
large  brownish  gland, 
which  lies  just  beneath 
the  fleshy  partition 
(diaphragm)  separa- 
ting chest  from  belly  Fig.  19.— Spittle  glands  of  the  intestine,  enlarged. 
(vide  fig.  21).  It  is 

composed  of  a  vast  number  of  tubes,  which  are  derived  from  a 
central  one,  being  given  off  from  this  latter  in  an  arborescent 
manner.  The  main  tube,  which  is  more  commonly  known  as 
the  bile  duct,  opens  into  the  small  intestine  below  the  stomach,  and 
the  ends  of  the  minutest  hollow  branchlets  are  closed  or  blind. 

Besides  this  tubular  apparatus  there  is  a  mass  of  soft  solid  material, 
which  gives  the  shape  to  the  organ,  and  with  the  veins  and  arteries 
which  are  present  also  fills  up  the  spaces  between  the  different  tubes. 
If  a  thin  slice  of  the  solid  matter  be  placed  in  the  field  of  the  micro- 
scope, it  presents  this  appearance  (fig.  20).  It  would  take  too  long  to 
enter  fully  into  the  structure  9f  tnis  organ,  which  is,  however,  most 
interesting  to  the  microscopic  anatomist.  The  fluid  formed  in  the 
liver  is  called  bile,  and  filters  from  the  blood  into  the  blind  pouch- 
like  ends  of  the  tube  branches,  from  which  it  flows  into  the  larger 
ones,  and  from  _  these  again  into  the  central  duct._ 

INow,  there  is  attached  to  the  liver,  and  opening  into  this  central 
duct,  a  small  bladder,  which  serves  as  a  reservoir  to  contain  the 


38  POPULAR  PHYSIOLOGY. 

bile  as  ii  is  gradually  distilled ;  for  we  find  that,  when  digestion  is 
not  going  on,  the  bile  does  not  flow  into  the  intestine,  but,  after 

having  passed  into  the 
bile  duct,  is  sent  back- 
wards into  this  reser- 
voir, the  gall-bladder 
(fig.  21). 

Some  physiologists 
have  thought  that  the 
liver,  besides  secreting 
bile,  altered  the  blood 
passing  through  it  by 
giving  it  sugar.  The 
notion  has  recently 
been  completely  upset, 
so  that  though  this 
organ  may  fulfil  other 
offices  besides  the  for- 
mation of  bile,  the 
latter  is  all  we  can 
maintain  to  take  place 
in  it. 

The  ancients  be- 
lieved that  the  liver 
exercised  a  powerful 
influence  over  the 
mind -and  our  common 

word  melancholy  is  derived  on  this  supposition  from  two  Greek 
words  which  signify  black  bile.  There  is  no  slight  reason  to  suppose 
that  the  state  of  the  mind  does,  in  some  measure,  depend  upon  the 
condition  of  the  liver ;  for,  if  this  organ  be  disordered  even  to  a 
small  extent,  the  effect  is  very  soon  observable  in  the  general  system. 
The  physician  will  tell  you,  "  Your  liver  is  out  of  order,  no  bile  is 
formed,  and  you  can't  in  consequence  digest  your  food ;"  but  push 
him  a  step  further,  ask  him  why,  and  he  is  floored  at  once.  If  we 
take  a  portion  of  boiled  meat— fat  and  flesh— and  place  it  in  a  vessel 
with  some  bile,  keeping  up  the  temperature  at  the  height  usual  in  the 
body,  about  98°  Fahrenheit,  we  shall  find  that  no  change  takes  place. 
Therefore,  it  is  evident  that  it  has  no  direct  action  on  the  food.  But 
if,  on  the  other  hand,  we  make  an  opening  into  the  gall-bladder,  so 
that  the  bile  passes  out  through  the  wound,  and  not  into  the  mtes- 
tine,  the  digestion  goes  on  very  imperfectly,  there  is  constipation  of 
the  bowels,  emaciation,  and  death.  This  experiment  has  been  per- 
formed on  dogs  with  the  result  I  have  given ;  but  strange  to  tell,  if 
the  animals  were  permitted  to  lick  the  wound,  and  so  swallow  the 
bile,  digestion  went  on  nearly  as  in  the  natural  state ;  hence  it  is  quite 
clear  that  the  bile  is  of  service^ 

It  is  also  injurious ;  for,  if  it  is  not  secreted,  it  accumulates  in 
the  system,  staining  the  skin  and  eyes,  and  terminating  in  the  ex- 
tinction of  life.  This  is  what  we  see  in  jaundice. 


Fig.  20.— Structure  of  Liver. 


COMPOSITION   AND   USE   OF  BILE. 


39 


Comparative  anatomy  is  no  mean  teacher  in  a  case  like  this.  It 
shows  us  that  in  the  lower  creatures  the  liver  conducts  the  bile 
into  the  stomach ;  whereas,  if  it  were  9nly  sewage  or  refuse 
matter,  it  would  be  poured  into  the  lower  division  of  the  gut,  and 
not  into  the  digestive  cavity,  where  it  might  be  absorbed,  and  if  effete 

Small  end  of 
Liver.   Stomach.    Gullet.  Pancreas.    Stomach. 


Gall  Bladder. 


Large  Intestine, 


Blind    end  of  •) 
Intestine.      $ 


Appendix.  - 


Spleen. 


Large  Intestine. 


Small  Intestine. 
—  Large  Intestine. 


Small  Intestine.  Rectum. 

Fig.  21.— Digestive  Apparatus  in  Man. 

might  act  poisonously.  All,  then,  that  we  can  say  of  the  bile  is,  that 
it  certainly  is  of  use,  but  that  we  have  not  yet  discovered  in  what 
way*  It  is  composed  of — 

Water 8SO>v 

Bile  matter    90  / 

Colouring  matter  )  -,  -  \'\\\  1000  parts. 

Fats    . . : \  \ 

Salts  15 ) 


1000 


40  POPULAR  PHYSIOLOGY. 

That  the  bile  does  not  pass  away  as  such  with  the  excrement  is 
certain,  for  the  quantity  of  sulphur  which  the  latter  contains  does 
not  amount  to  one-eighteenth  of  what  is  poured  into  the  intestine 
with  the  liver  fluid.  What  becomes  of  it?— that  is  a  mystery  to 
physiologists. 

Next  we  come  to  the  consideration  of  the  sweetbread  or 
pancreas  (from  two  Greek  words,  meaning  all  flesh).  This  is  a 
long  flat  gland,  lying  on  the  back  of  the  stomacli,  and  whose 
structure  we  need  not  here  discuss,  as  it  is  similar  to  that  of  the 
spittle  glands  already  described.  The  channel  which  conveys  away 
the  swee.tbread's  secretion,  opens  into  the  small  gut  below  the 
stomach,  and  exactly  opposite  the  opening  of  the  bile  duct. 

The  liquid  formed  by  this  organ  is  transparent,  viscid,  and  alkaline, 
strongly  resembling  the  saliva  in  these  particulars.  Its  action  is 
confined  to  the  fatty  and  starchy  matters  of  the  food.  It  converts 
the  starch  into  sugar,  and  by  causing  the  oily  substances  to  be 
reduced  to  a  state  of  very  fine  division,  renders  them  soluble.  How 
is  this  demonstrated  ?  Remove  from  the  pancreas  of  a  dog  a  quantity 
of  the  secretion,  place  it  in  a  glass  vessel  with  some  oil  and  starch, 
maintain  a  temperature  of  100  degrees  Fahrenheit,  and  after  some 
hours  y9u  will  find  the  starch  turned  into  sugar,  and  the  oil  changed 
to  a  whitish  liquid,  called  an  emulsion. 

But  this  is  not  all.  M.  Bernard  has  proved  conclusively  that  the 
above  is  the  office  of  the  pancreatic  fluid.  Tiie  rabbit  was  the 

animal  he  selected  for  his  experi- 
ment, because  in  it  the  canal  of 
the  sweetbread  opens  into  the  gut 
much  lower  down  than  that  of  the 
liver  (fig.  22).  He  tied  the  intes- 
tine at  a,  having  previously  intro- 
duced a  Quantity  of  fatty  and  starchy 
food,  and  he  also  tied  it  at  b,  thus 
leaving  a  sac  of  gut,  c,  between  the 
two  knots,  into  which  sac  the  se- 
cretion of  the  sweetbread  was 
carried.  After  a  certain  number  of 
hours  the  animal  was  killed,  and 
the  food  was  examined,  when  it  was 
found  that  the  fat  had  been  in  some 
measure  dissolved  and  absorbed, 
and  the  starch  was  to  a  great  ex- 
tent converted  into  sugar.  The  pancreatic  juice  consists  of 


Gut. 


<"       Duct  of 
(.  Sweet-bread. 


Gut. 


Fig.  22. 


Water 900 

A  peculiar  substance, 

called   Pancreatine    00 
Mineral  Salts   ...    10 

1000 


in  1000  parts. 


Before  we  come  to  the  subject  of  digestion  as  a  whole,  let  me  observe- 


LENGTH   OF  INTESTINE.  41 

that  the  intestinal  canal  is  not  dependent  on  the  general  nervous 
system  for  its  supply  of  nervous  power.  A  German  anatomist  has 
lately  discovered  a  most  complete  series  of  nerve  centres,  situate 
between  the  layers  of  the  guts  along  their  entire  length ;  and  though, 
doubtless,  this  luckless  individual  will  receive  many  a  blow  ere  his 
views  are  recognized,  I  have  great  confidence  in  the  ^truthfulness 
of  his  observations.  The  intestines  do  not  lie  loosely  in  the  belly, 
but  are  gathered  up  by  a  membrane  attached  to  them  and  the  back- 
bone. (Fig.  25.) 

Pendulous  Palate. 


Base  of  the  Cranium. 


Pharynx. 


Gullet. 


..Tongue. 

.  Salivary  Glands. 
.  Tongue  Bone. 


.... Larynx. 


Thyroid  Gland. 


Trachea  or  Windpipe. 


Fig.  23.— Vertical  Section  of  the  Throat  and  Mouth. 

The  intestinal  canal  is  exceedingly  long  in  herbivorous  animals ; 
being  in  the  sheep  twenty-eight  times  the  length  of  the  body.  In 
flesh-eaters,  on  the  contrary,  it  is  extremely  short ;  thus,  in  certain 
blood-sucking  bats  it  is  little  more  than  the  length  of  the  creature 
itself.  The  reason  of  this  difference  is  obvious ;  in  carnivora  the 
food  is  easily  digested,  and  the  process  takes  place  in  the  stomach  ; 
whilst  in  those  animals  feeding  on  plants,  the  main  part  of  the 
digestive  process  is  gone  through  in  the  intestine. 

In  man  we  find  the  alimentary  tract  intermediate  in  dimensions,  a 
circumstance  which  is  clearly  indicative  of  the  kind  of  food  required 
by  the  human  race,  [viz.,  a  mixed  one,]  and  is  another  fact  to  quash 
vegetarianism.  Man's  intestinal  canal  is  about  five  times  the  length 
of  his  body,  which  the  reader  will  recollect  in  association  with  Aber- 
nethy's  remark  to  the  lady,  "  You'll  please,  ma'am,  to  remember  that 
you  have  twelve  yards  of  guts." 


42  POPULAR  PHYSIOLOGY. 

Having  now  gone  over  the  individual  wheels  and  levers  of  the 
complex  digestive  mechanism,  we  are  in  a  better  position  to 
study  its  movements  collectively.  How  shall  we  begin  ?  Shall  we 
observe  the  bolus  during  its  transmission  through  the  tstkmi  faucium, 
noticing  the  approximation  of  the  palato-glossi,  the  elevation  of  the 
laryngeal  apparatus,  depression  of  the  epiglottis,  and  tensed  condition 
of  the  velum  pendulum  palati?  No,  "no  more  of  this,  Hal,  an* 
thou  lovest  me." 

Reader,  step  down  with  me  to  yon  tavern,  and  we  shall  have  a 
chop  and  roast  potatoes  and  glass  of  "  bitter  "  together.  What !  you 
really  will  consent  to  so  plebeian  an  undertaking  ?  Good !  Now, 
whilst  you  are  eating  and  resting — as  you  con  the  last  Punch,  I  shall 
explain  to  you,  by  the  help  of  my  physiological  "  Bradshaw,"  the 
route  of  that  same  mutton  chop  and  those  roast  potatoes,  shewing  you 
how  far  they  travel  together,  and  by  what  lines  they,  after  separation, 
arrive  at  their  respective  destinations. 

Firstly,  the  mixture  of  flesh,  fat,  P9tatoes,  and  beer  having  been 
well  chewed,  and  mingled  with  saliva,  is  turned  back  by  your 
tongue  into  your  throat  (fig.  23),  where  it  is  caught  by  the  muscle 
of  the  gullet,  and  gradually  forced  down  into  the  stomach.  (There, 
that  piece  of  potatoe  was  too  large,  and  you  feel  it  all  the  way 
down,  as  if  it  was  a  bit  of  stone  !)  Secondly,  the  mass  has  reached 
the  digestive  bag ;  now  the  entrance  and  exit  openings  of  this 
sac  close  on  it,  so  it  is,  pro  tempore,  imprisoned.  The  stomach 
immediately  begins  contracting,  and  the  food,  together  with  the 
gastric  juice,  is  turned  round  and  round  from  left  to  right.  Whilst 
this  is  going  on,  the  flesh,  and  the  albumen  of  the  potatoes  are  being 
made  quite  fluid,  and  as  quick  as  they  are  made  so,  pass  into  the 
veins  of  the  stomach,  penetrating  the  wall  of  these  by  endosmose 
(vide  chap.  I.).*  The  beer  has  passed  away  in  a  similar  manner,  till 

*  The  velocity  with 
which  the  blood  tra- 
vels along  the  vessels 
of  the  stomach  has 
much  to  do  with  the 
absorption  of  liquids. 
This  may  be  proved 
experimentally  in 
the  following  man- 
mer :— Let  apiece  of 
intestine,  a,  be  at- 
tached at  each  end, 
as  shown  in  the  dia- 
gram, and  placed  in 
a  vessel  containing  a 
strong  solution  of 
sugar,  d ;  if,  then, 
water  be  caused  to 
flow  from  the  funnel 
I,  through  the  intes- 
tine and  tube,  c,  into 


SOLUTION   OF   OIL. 


there  is  nothing  left  but  the  starch  of  the  potatoes  and  the  fat.   This 
latter  is  contained  in  little  bladders  of  fleshy  material,  which  are  now 


Fig.  24. — The  Chest  opened,  to  show  the  Backbone,  and  posterior  ha'f 
of  the  Ribs,  with  the  great  Lacteal  Vessels.  i.  Main  trunk  of  the  Lacteal 
Tree.  2.  Lacteal  vessels  of  the  body  generally.  3.  Receptacle  of  the  Chyie. 
4.  Junction  of  the  Veins  of  the  Shoulder  and  Neck,  and  connection  of  the  mam 
Trunk  with  the  Vein  of  the  Left  Shoulder. 

dissolved  by  the  gastric  juice,  and  follow  the  beer  and  potato 
albumen.  Finally,  just  as  the  stomach  has  ceased  revolving,  there 
remain  in  it  but  oil,  starch,  and  a  few  bits  of  tendon ;  these  it  has 


another  vessel,  e,  it  •will  be  found, — 1st.  That  a  portion  of  the  saccharine 
solution  has  passed  into  e,  and  2nd.  That  the  greater  the  rapidity  of  the 
current,  a  c,  the  greater  has  been  the  amount  of  sugar  absorbed. 


44 


POPULAR  PHYSIOLOGY. 


no  jurisdiction  over,  so  the  portcullis  is  opened,  and  they  are  trans- 
ported, after  three  hours'  detention,  to  the  intestine.  Here  they  are 
met  by  the  pancreatic  juice  in  all  its  alkalinity,  and  become  speedily 
transformed!,  the  starch  into  sugar,  the  oil  into  emulsion,  and  both 
constitute  a  white,  milky  fluid,  called  chyle,  which  is  quite  soluble, 
and  is  only  awaiting  my  description  of  the  absorbing  organs  prior  to 
being  received  into  the  system. 

I  have  spoken  before  of  tubes  called  lacteals,  which  are  found  in 
the  villi  of  the  intestines.     These  lacteals  are  but  the  terminal 

Aorta.  Thoracic  Canal.  Lacteal  Glands. 


Roots  of  the  Lacteals. 
Intestine. 


Lacteal  Vessels.    Membrane  sustaining  Intestine. 
Fig.  25. 

branches  of  a  great  tree,  whose  root  is  at  the  junction  of  the  two 
principal  veins  at  the  left  side  of  the  neck  (fig.  24).  The  stem 
of  this  tree  lies  close  to  the  backbone,  as  it  passes  from  the  neck  to 
the  belly,  and  does  not  assume  the  arborescent  form  till  it  has  reached 
the  membrane  which  sustains  the  intestines  (fig.  25).  It  then 
divides  and  subdivides,  the  divisions  having  knots  on  them  called 
mesenteric  glands,  and  finally,  the  last  branchlets  end  each  in  a  little 
villus,  which  may  be  regarded  as  the  leaf  (fig.  26).  As  the  foliar 
parts  of  a  plant  abstract  certain  substances  from  the  surrounding 
air,  so  do  ^the  lacteal  leaflets— the  villi — remove  from  the  intestine 
the  nutritious  chyle  which  it  contains. 

These  little  villi  suck  up  as  it  were  the  fluid  sugar  and  fat ;  but  how 
these  penetrate  them  is  still  unsolved.  One  set  of  observers  says,  the 
lacteals  have  open  ends,  and  so  the  chyle  passes  into  them  ;  another, 


BRUNNER'S  GLANDS— DIGESTIVE  FLUIDS. 


45 


that  it  enters  in  obedience  to  the  law  of  endosmose.  I  confess  I 
incline  to  the  latter  supposition,  but  whichever  view  be  correct,  one 
thing  is  certain,  it  does  gain  an  entrance ;  for,  if  a  dog  be  killed  a 

short    time    after   a  meal  of 
-T7T>v  bread  and  butter,  and  the  belly 

opened,  the  chyle  by  reason  of 
its  whiteness  can  be  seen  tra- 
versing the  branchlet  lacteals 
towards  the  main  stem,  from 
which  it  is  afterwards  poured 
into  the  veins  above-mentioned. 
If  in  the  confusion  conse- 
quent upon  the  discharge  of 
the  fatty  and  starchy  matters 
from  the  stomach,  any  particles 
of  undissolved  flesh  happen  to 
Fig.  26.-Diagram  explaining  the  structure  have  made  their  escape,  they 
of  a  viiius ;  «,  outer  covering  of  cells ;  b,  a  are  placed  under  the  protection 

single  cell;  c,  delicate  membrane  on  which  of  the  juices  of  Brunner's 
the  cells  rest ;  d,  Blood-vessel ;  e,  end  of  a  glands  (fig>  19^  Tjiege  yery 

soon  provide  them  with  the 

necessary  passports  to  the  veins  of  the  intestine ;  and  eventually 
the  refuse  substances,  bits  of  tendon,  &c.,  are  expelled.  Of  course, 
as  I  have  heretofore  stated,  the  bile  is  also  poured  into  the  gut  during 
digestion,  but  as  we  do  not  understand  its  actions,  I  omitted  it,  to 
avoid  confusion. 

The  period  required  for  the  digestion  of  various  forms  of  meat  has 
been  estimated  by  an  American  physician,  and  is  as  follows  : — 

Kind  of  food.  hours,  min.  Kind  of  food.  hours,  min. 

Pig's  feet..     .  1      0  Roast  beef        ...  30 

Tripe 10  Roast  mutton    ...  3    15 

Trout,  broiled .  1    30  Broiled  veal      ...  40 

Venison  steak .  1    35  Boiled  salt  beef        .  4    15 

Milk 20  Roast  pork        ...  5    15 

Roast  turkey  .  2    30 

It  is  not  a  little  surprising  to  note  the  quantities  of  the  different 
digestive  fluids  poured  into  the  intestine  during  the  twenty-four  hours. 
In  weight,  the  sum  of  these  vastly  exceeds  that  of  the  excremen- 
titious  matters.  The  following  is  the  amount  of  each  secretion 
formed  in  the  adult  in  the  course  of  the  day,  according  to  the  best 
authorities : — 


Saliva      
Gastric  juice  
Bile       

Pancreatic  juice  
Intestinal  do. 

Ib.    oz. 
.     3      8 
14      0 
3      8 
0      6 
0      7 

21    13 


46  POPULAR  PHYSIOLOGY. 

The  total  is  almost  astounding,  when  we  consider  the  small  amount 
of  food  which  is  required  by  a  full-grown  man,  accustomed  to  out- 
door exercise ;  the  entire  amount  of  solid  food  necessary  during 
twenty-four  hours  being  about  two  and  a  half  pounds.  Thus — 

Ib.   oz. 

Meat     0    16 

Bread 0    19 

Butter 0      4 

2      7 

Of  course  the  actual  weight  of  nutritious  aliment  demanded  will 
be  dependent  on  the  state  of  the  constitution,  habits  of  the  indi- 
vidual, and  various  other  circumstances  sufficiently  obvious.  Hosts 
of  people  now-a-days  complain  of  their  stomachs.  'You  hear  that  fish 
disagrees  with  one,  vegetables  with  another,  cheese  with  a  third,  and 
so  on,  and  the  term  dyspepsia  (a  compound  of  two  Greek  words,  sig  • 
nifying  difficult  digestion)  has  been  applied  to  this  condition. 

If  the  goodfolk  who  so  very  patiently  submit  to  having  their  stomachs 
electroplated  by  the  drugs  of  quack  physicians,  and  allow  themselves 
to  be  stewed  down  in  those  monster  human  cooking  apparatuses, 
Turkish  baths,  would  only  adopt  the  measures  dictated  by  common 
sense,  I  promise  them  they  should  know  much  less  of  dyspepsia  than 
they  do  at  present.  For  example,  my  good  friends,  do  not,  as  the 
great  Scotch  surgeon  said  to  the  Yankee, "  bolt  your  food  like  an 
alligator,"  and  do  not  overload  your  stomachs.  Especially  observe 
this  practice :  always,  if  possible,  rest  for  half  an  hour  after  each  meal. 
Take  a  good  sponge-bath  every  morning-  most  animals  wash  them- 
selves, but  man  seldom  does  so.  I  should  like  to  know  how  many 
men  and  women  clean  themselves  every  day  in  the  week. 

The  skin,  as  I  shall  show  you  when  I  come  to  it,  is  a  great  gland  of  as 
much  importance  as  the  liver  or  kidneys;  and  yet  how  much  neglected! 
lam  firmly  convinced  that,  did  men  regularly  wash  their  bodies  on 
rising  every  morning,  the  number  of  dyspeptic  cases  would  be  reduced 
to  one-half.  And  dyspepsia  is  a  demon,  which  is  at  the  bottom  of 
many  a  crime  we  give  other  causes  credit  for.  It  unfits  a  man  for 
physical  exertion,  as  well  as  mental,  and  by  unnerving  him,  not  un- 
frequently  is  the  fiend  which  urges  him  on  to  suicide.  Again,  then, 
let  me  repeat,  clean  yourselves.  "  Cleanliness  and  godliness  "  have 
ever  been  espoused.  Too  much  attention  cannot  be  devoted  to 
the  bowels,  the  neglect  of  which  plunges  the  careless  man  into 
fevers,  indigestion,  kidney  disease,  and  piles  —  ay,  piles — those 
Harpies  of  middle  age  !  I  can  add  nothing  in  force  to  the  anecdote 
of  Abernethy  regarding  this  subject.  "  A  mother,  sending  her  son 
for  the  first  time  to  London,  remarked,  '  My  boy,  in  the  first  place, 
have  the  fear  of  God  always  before  your  eyes,  and  in  the  second,  be 
sure  and  keep  your  bowels  open'  " 


THE  BLOOD.  47 


CHAPTER    VII. 

The  blood.  Its  color,  microscopic  charactei's  and  composition — Use  of 
fibrine — Physiology  and  medico-legal  inquiries— Cause  of  the  color  of  the 
blood — How  does  venous  blood  differ  from  arterial  ? — Views  of  Liebig 
— Respective  actions  of  carbonic  acid  and  oxygen  upon,  the  blood — 
Blood  corpuscles  die  at  the  rate  of  20,000,000  per  second  !— Capillaries 
— Difference  between  arteries  and  veins — The  circulation  of  the  blood 
— Structure  of  the  heart — Auricles,  ventricles,  and  valves — Force- 

SLimp  action  of  the  heart — Other  forces  concerned  in  the  circulation — 
ffice  of  the  valves  in    veins — The  pulse — Sounds  of  the  heart — The 
latter  a  key  to  the  state  of  the  circulatory  organ — Action  of  the  mind 
upon  the  pulse — Average  number  of  beats  in  the  infant,  adult,  and 
aged— Velocity  of  the  blood— Rhythm  of  the  heart — Simile  of  Harvey's 
— M.  Groux— Dublin  experiments— Use  of  a  knowledge  of  physiology  to 
;-  the  physician — Colonel    Townsend — Proof  of  the  circulation — Barber 
Surgeons  and  Samuel  Pepys— Literature  of  the  subject — Did  Harvey 
discover  the  circulation  ? 

WE  have  seen  how  the  crude  materials  are  converted  into  albumi- 
nous, oily,  and  starchy  substances,  required  for  the  manufacture  of  the 
tissues  and  maintenance  of  the  bodily  heat.  We  have  yet  to  consider 
in  what  form  these  substances  are  best  suited  to  rebuild  the  tissues 
of  the  frame,  and  also  the  mode  in  which  they  are  carried  to  the 
distant  regions  of  the  animal  economy.  Thus,  in  the  first  place,  we 
shall  enter  upon  the  study  of  the  blood  itself,  and  in  the  second  upon 
the  consideration  of  the  way  in  which  the  blood  is  conveyed  to  the 
tissues  and  the  power  employed  in  its  conveyance— in  one  word,  the 
circulation. 

The  blood  you  will  tell  me  is  a  red  liquid  ?  You  are  wrong ; 
it  is  perfectly  colourless.  It  is  found  in  every  portion  of  the  body, 
passing  through  billions  of  little  canals  so  close  to  one  another 
that  the  naked  eye  cannot  perceive  any  spaces  between  them.  Let 
us  collect  some  of  the  blood  which  has  just  flown  from  a  wound,  and 
place  it  in  a  tumbler.  After  some  hours,  we  see  it  consists  of  a  red 
firm  jelly  of  the  shape  of  the  vessel,  lying  at  the  bottom  ;  and  a  clear 
liquid  like  white  of  egg  floating  above  it ;  the  first  is  the  clot,  the 
second  the  serum. 

Now  if  we  still  further  examine  this  clot,  by  taking  a  very  thin 
slice,  washing  it  well  in  water,  and  placing  it  under  the  microscope, 
we  perceive  that  it  is  formed  of  a  most  complicated  net-work 
of  white  fibres  [collectively  termed  fibrine],  which  entangle  in 
their  meshes  several  little  bi-concave  scarlet  disks.  These  latter 
are  the  blood  corpuscles,  and  to  them  is  due  the  scarlet  colour 
of  the  blood.  They  are  very  small  and  quite  imperceptible  to  the  un- 
assisted eye ;  measuring  only  about  the  sfojth  of  an  inch  across.  These 
corpuscles  are  very  indestructible,  and  may  be  extracted  from  the  blood 
stains  on  weapons,  upon  which  the  fluid  has  remained  for  many 


48  POPULAR  PHYSIOLOGY. 

years ;  on  which  acc9unt,  as  the  reader  must  be  aware,  the  micro- 
scopist  is  able  to  give  material  assistance  to  the  lawyer  in  many 
criminal  investigations. 

The  supernatant  liquor  or  serum  is  composed  of  water,  white 
of  egg,  and  salts,  with  a  trace  of  fat.  That  it  contains  white  of 
egg  is  evident  from  the  fact,  that  on  boiling  it  becomes  of  an 
opaque  white  and  more  or  less  solid.  The  fibrine  is  fluid  only  in 
the  oody,  for,  as  soon  as  the  blood  is  drawn  from  the  wound, 
it  clots,  or,  as  is  more  usually  said,  coagulates,  forming  the  reticulation 
described  above.  What  a  grand  provision  is  this  power  of  clotting 
in  blood !  It  is  by  virtue  of  this  tendency  that  small  wounds 
close  of  themselves  ;  a  natural  sticking-plaster  being  developed  by 
the  fibrine,  which  plugs  up  the  mouths  of  the  incised  arteries.  If  it 
were  not  for  the  fibrine,  the  slightest  cut  would  prove  fatal ;  not  liga- 
tures, nor  tourniquets,  nor  all  the  strange  appliances  of  surgery  could 
prevent  the  patient  bleeding  to  death.  We  do  not  vet  kno\y  for  certain 
what  the  fibrine  is.  Chemical  analysis  shows  it  to  be  very  like  albumen 
in  composition,  but  then  albumen  cannot  spontaneously  convert  itself 
into  a  substance  which  has  many  of  the  features  of  a  tissue.  Some 
assert  that  it  is  a  refuse  material,  resulting  from  the  decay  of  certain 
structures.  It  is  much  more  likely  that  it  is  albumen  on  its  way  to 
tissue  (tendon  for  example),  which,  when  drawn  from  the  vessels, 
exhibits  to  the  best  of  its  intrinsic  ability  a  tendency  to  form  some 
structure,  by  giving  rise  to  the  net-work  I  have  alluded  to.  How  it  is 
kept  in  solution  in  the  body  is  also  a  mystery.  Some  say  it  is  by  the 
action  of  ammonia  •  others  that  it  is  due  to  its  motion  and  contact  with 
living  animal  membrane ;  and  some  consider  that  as  fast  as  it  is  formed 
it  is  made  into  tissue,  and  that  what  we  get  in  blood  is  only  that 
which  was  developed  the  moment  previously. 

However,  no  matter  how  true  or  incorrect  these  views  may  be,  one 
thing  is  certain ;  living  blood  does  coagulate.  You  may  say,  oh,  what 
matter  whether  it  does  or  not  ?  No  fact  in  science  is  unimportant,  and 
this  more  particularly.  It  is  of  the  greatest  possible  value  in  a  medico- 
legal  point  of  view.  JFor  example,  a  man  is  found  lying  on  the  highway 
with  his  throat  cut ;  circumstances  indicate  that  he  has  arrived  at  his 
death  by  other  means,  and  that  the  incision  in  the  neck  has  been  made 
as  a  ruse  to  throw  the  public  off  their  guard.  The  case  then  turns  on 
this  question,  how  can  you  determine  whether  the  wound  was  inflicted 
before  death  or  after  ?  The  physiologist  replies  :  if  before  death,  the 
blood  will  be  clotted  ;  but  if  after,  there  will  DC  no  coagulation.  There 
being  no  clot  detected,  the  conclusion  follows  that  death  was  caused 
in  some  other  manner  than  that  indicated  by  the  injury  to  the  throat. 

'795  of  water 
The  blood  of  a  man  I         "  SKen  * 


10     stone    heavy 
weighs  ISlbs.j  and 


contains  in  1,000  parts 


fatty  matter 


„  fibrine 
1,000 


CAUSE  OF  THE  COLOUR  OF  BLOOD.  49 

Besides  the  constituents  enumerated  in  this  table,  there  are,  in 
small  quantity,  round  granular  vesicles,  larger  than  the  red  corpuscles, 
and  which  have,  from  their  pale  whitish  colour,  received  the  distinc- 
tive appellation  of  white  blood-globules.  These  are  the  parents  of 
the  red  ones,  which,  by  the  way,  they  set  free  in  dying.  It  is  a 
curious  thing  that  a  fair  mother  should  have  a  coloured  offspring,  yet  so 
it  is  in  this  case. 

The  red  globules  are  found  by  chemists  to  contain  a  large 
quantity  of  iron ;  and  it  is  really  by  this  iron  that  the  scarlet  tint 
of  the  blood  is  caused.  Baron  Liebig  has  given  satisfactory 
proof  of  this.  It  is  true  his  opinion  has  been  assailed  furiously, 
but  I  think  that  his  opponents  have  had  the  worst  of  the 
battle.  I  believe  his  ideas  on  this  question  are  in  the  main  correct ; 
though  I  am  not  prepared  to  be  the  champion  of  their  details. 

I  conceive  that  the  iron  is  in  combination  with  the  white  of  egg 
substance,  which  also  enters  into  the  composition  of  the  cor- 
puscles ;  and  that  the  two  together  form  a  new  compound  con- 
sisting of  albumen,  iron,  and  soda— not  merely  mixed,  but  combined 
to  form  a  substance  differing  from  any  of  the  three.  In  the  same 
manner  as  the  letters  o  d  g,  if  put  loosely  together,  as  in  odg, 
form  no  word ;  but  if  arranged  as  d  o  g,  or  G  o  d,  two  very  distinct 
sounds,  differing  from  the  three  letters,  and  not  mere  mixtures, 
result. 

Let  us  see  why  this  is  probable.  Blood  is  not  always  red,  it  is 
only  so  as  a  rule  in  the  arteries ;  for  in  the  veins  it  assumes  a  bluish 
purple  hue.*  The  origin  of  this  change  of  colour  I  shall  more  fully 
explain,  under  the  head  of  respiration  ;  here  I  can  only  say  that  the 
venous  blood  carries  in  it  a  great  quantity  of  that  foul  air  called 
carbonic  acid.  This  latter  has  been  produced  in  the  wear  and  tear 
of  the  tissues,  and  is  believed  to  be  the  cause  of  the  alteration  in 
the  colour  of  the  vital  fluid  as  it  flows  through  the  veins. 

If  we  pass  through  a  portion  of  blood,  a  current  of  carbonic 
acid  gas,  it  is  at  once  deprived  of  its  scarlet  hue,  and  becomes  of  a 
bluish  purple  ;  if,  on  the  other  hand,  we  force  through  it  a  stream 
of  fresh  air  its  original  colour  is  restored.  Now,  please  don't 
be  impatient ;  we  are  coming  to  the  point !  We  have  taken  albumen, 
soda,  and  iron,  and  made,  by  artificial  means,  an  albuminate  of  iron. 
In  the  first  place  we  pass  through  this,  carbonic  acid,  and  it  assumes 
a  greenish  red  colour ;  and  in  the  next  we  expose  it  to  the  action  of 

*  A  celebrated  French  physiologist  has  recently  stated  that  the  veins 
do  not  always  contain  dark-coloured  blood  ;  that  when  the  vein  is  convey- 
ing the  fluid  from  a  muscle  which  is  being  exercised,  then  the  blood  is 
purplish,  but  when  the  muscle  is  quiescent  then  it  is  scarlet.  Also  that 
when  the  blood  is  carried  away  by  the  veins  from  a  gland  (spittle  gland, 
for  example)  which  is  forming  its  secretion,  it  is  usually  red,  and  vice  versd, 
This  is  for  the  following  reason  •  the  venous  blood  from  the  exerted  muscle 
contains  worn-out  matter ;  that  from  the  muscle  at  rest,  none.  The  venous 
fluid  from  the  inactive  gland  contains  a  great  deal  of  effete  matter  ;  that 
from  the  secreting  gland  not  so  much. 

E 


50  POPULAR  PHYSIOLOGY. 

the  atmosphere,  and  find  it  has  received  a  ruddy  hue  ;  therefore,  we 
conclude — and  I  think  not  unfairly — that  the  change  of  colour  in  the 
blood  is  due  to  the  influence  of  carbonic  acid  upon  the  albuminate  of 
iron,  which  it  contains. 

The  opposite  school  of  physiologists  asserts  that  the  cause  is 
a  physical  one,  and  not  chemical;  that  in  the  venous  blood  the 
corpuscles  become  swollen,  and,  by  breaking  the  light  which  tra- 
verses them,  appear  dark,  whilst  in  arterial  blood  they  shrivel  up, 
and  appear  lighter  in  colour.  This  is  a  mere  supposition,  unsupported 
by  actual  observation.  Both  sides  agree  in  this  :  that  their  office  is 
to  carry  the  pure  air  (oxygen)  from  the  lungs  to  the  different  portions 
of  the  body,  and  bring  away  to  the  lungs  from  the  distant  regions, 
the  effete  gas  (carbonic  acid),  resulting  from  the  decay  of  the 
system. 

It  is  thought  that  the  blood  corpuscles  live  but  for  a  very  short 
period,  and  it  has  been  computed  that  at  every  beat  of  the  heart  twenty 
millions  of  these  little  organisms  cease  to  exist.  How  few  think  that 
there  are  bells  within  their  bosoms  tolling  the  death-knell  of  so  many 
living  beings !  Verily  "  There  are  more  things  in  heaven  and  earth 
than  are  dreamt  of  in  your  philosophy,  Horatio."  There  is  no  sub- 
ject in  physiology  more  interesting,  or  about  which  there  has  been 
more  confusion  than  that  of  the  blood.  It  has  engaged  the  attention 
of  philosophers  from  a  very  early  period,  and  many  and  curious  have 
been  their  speculations  regarding  the  nature  and  circulation  of  this 
fluid. 

Ere  we  plunge  into  the  "  media*  res  "  of  the  circulation,  we  must 
glance  at  the  system  of  tubes  through  which  the  blood  is  con- 
veyed. These  are :  Firstly,  arteries,  or  vessels,  which  carry  the  blood 
from  the  heart  to  the  furthest  portions  of  the  frame  (fig.  27) ;  secondly, 
the  microscopic  channels  which  exist  in  every  part  of  the  body — the 
capillaries* — ending  on  one  side  in  the  arteries,  and  on  the  other  in 
(thirdly)  the  veins,  which  bring  the  blood  from  the  tissues  to  the 
heart,  and  so  complete  the  circle.  The  arteries  are  quite  elastic, 
being  in  chief  part  composed  of  a  material  whose  properties  are 
similar  to  those  of  india-rubber.  The  capillaries  have  no  distinct 
coats  (?),  being  only  passages  tunneled  in  the  soft  parts.  The  veins  are 
not  elastic,  and  are,  m  addition,  provided  with  valves  (like  those  of  a 
pump),  which  open  towardsi\\e  heart. 

The  system  of  tubing  just  mentioned  starts  from  the  great  central 
reservoir — the  heart— which  is  not  only  the  cistern  from  which  the 
supply  to  the  different  parts  of  the  body  takes  its  origin,  but  also 
the  centre  of  the  propelling  power,  by  which  the  blood  is  driven 
through  the  arteries.  The  heart,  then,  holds  the  same  relation  to  the 
arteries  that  the  steam-engine  does  to  the  water-piping  of  our  large 
towns— it  pumps  the  fluid  on  through  the  various  branches. 


*  From  the  Latin  word  Capilla  (a  hair) — a  very  improper  designation, 
for  the  vessels  thus  called  are,  some  of  them,  so  minute,  that  hundreds  of 
them  placed  side  by  side  would  not  be  as  large  as  a  single  hair. 


THE  BLOOD-VESSELS. 


5L 


Temporal 
Artery. 


Artery  of 
Foot. 


Hind  Ar- 
tery of  Leg. 


^.«-  Artery  of 
Ankle. 


Fig.  27.— Arterial  System  in  Man. 

What  is  meant  by  the  expression  "  circulation  of  the  blood  ?"  Simply, 
that  the  fluid  moves  in  a  sort  of  circle— that  is  to  say,  it  leaves  a 

E2 


52 


POPULAR  PHYSIOLOGY. 


certain  locality,  travels  round  the  body,  and  returns  to  the  spot  from 
which  it  set  out.  Let  us  say  the  blood  leaves  the  heart  ;  it  is  expelled 
from  this  organ  through  the  first  branch  or  aorta,  and  afterwards 
through  its  numerous  divisions  and  sub-divisions,  till  it  reaches  some 
distant  part—  the  foot,  for  example.  Here  it  passes  from  the  arteries 
into  the  capillaries  (these  perforate  every  portion  of  the  skin,  muscles, 
&c.),  and  undergoes  many  changes,  giving  up  the  pure  materials  it  con- 
tains, to  the  tissue,  in  order  to  repair  it,  and  receiving  in  return  the  used 
up  substances  resulting  from  decay.  It  next  enters  the  veins,  and, 
from  the  fact  of  its  being  impregnated  with  worn-out  tissue  (carbonic 


Vein  of  the  Arm. 


Right  Lung. 


Artery  of  the  Arm. 
Vein  of  the  Amu 


Left  Lung. 


Fig.  28.— Lungs,  Heart,  and  Principal  Vessels  in  Man.— vj,  rj,  the  two  Jugular 
Veins;  t,  the  Windpipe ;  od,  the  Right  Auricle;  vd,  the  Right  Ventricle ;  vg,  the 
Left  Ventricle ;  a,  the  Aorta ;  we,  the  great  Vein  which  brings  impure  blood  from 
the  Abdomen. 

acid,  and  such  like),  assumes  the  purplish  tint.  Next,  it  travels  along 
these— flowing  from  the  smaller  canals  into  the  larger  ones,  until  at 
last  it  reaches  the  heart,  from  which  it  started.  This  is  a  rough 
outline  of  the  circulation ;  but  the  complete  one  is  a  little  more 
complex. 

The  heart  is  a  somewhat  conical  mass  of  flesh  (fig.  28),  lying  in  the 
chest  between  the  two  lungs.  From  its  broad  end  the  great  arteries 
arise,  and  its  point  is  turned  towards  the  left  side,  and  during  pulsation 
strikes  rather  forcibly  against  the  flesh  between  the  fifth  and  sixth 


THE   CAVITIES  OF  THE  HEART.  53 

a-ib,  or  just  below  the  nipple.  It  is  popularly  represented  as  bein"-  of 
the  same  form  as  that  painted  on  playing  cards  ;  this  is  a  great  error 
and  I  should  very  much  like  to  know  who  originated  it.  If,  however' 
you  would  wisl^  to  get  an  idea  of  the  form  of  the  human  heart' 
,  examine  that  of  the  sheep,  which  is  similar  in  character.  The 
heart  is  not  a  simple  bag ;  it  is,  on  the  contrary,  a  most  complicated 
apparatus,  having  four  distinct  cavities,  whose  openings  of  communi- 
cation are  provided  with  valves,  admirably  fitted  to  prevent  the 
return  of  blood  from  one  to  the  other.  It  is  better  to  say  there 
are  two  pairs  of  cavities  than  four  distinct  compartments  for  in 
each  pair  the  two  cavities  are  like  those  of  the  opposite  side.  These 
chambers  are  termed  the  auricles  and  ventricles  of  each 'side  re- 
spectively. 


Great  Upper  Vein.  Art.  Pulm.  Aorta.  Art.  Pulm. 

•Great  Lower  Vein.  — iC^^^S  Hw/ 

XxlBB^y     ~~          •  Left  Ventricle. 

Partition.  Aorta. 


It  seems  as  if  the  heart  was  composed  of  two  organs,  which  are 
fused  together;  and  when  describing  the  course  of  the  blood  it 
renders  the  account  simpler  to  speak  of  two  hearts  —  the  right 
find  left.  _  Each  heart  (or  more  correctly  each  side  of  the  heart) 
is  divided  into  two  chambers— an  upper  and  lower— the  first  receives 
the^  blood  from  the  great  vein,  or  veins,  and  pours  it  into  the  second, 
which  then  forces  it  away  through  an  artery  (fig.  29).  To  anyone  who 
has  studied  hydraulics  an  objection  here  presents  itself,  viz.,  when  the 
<!ower  chamber  is  expelling  the  blood,  why  does  not  the  liquid  flow 
back  into  the  upper  one  as  well  as  into  the  artery  ?  For  this  reas9n : 
the  orifice  through  which  the  bWd  flows  is  guarded  by  a  beautiful 
membranous  valve,  which  opens  into  the  lower  cavity ;  but  when 
this  latter  closes  on  the  fluid,  in  forcing  it  forwards  the*  valve  shuts, 


54  POPULAR,  PHYSIOLOGY. 

and  so  the  blood  reaches  the  artery,  having  been  prevented  passing 
backwards.  The  upper  chamber  is  called  an  auricle,  the  lower  a 
ventricle  ;  and  since  there  are,  as  it  were,  two  hearts,  it  follows  that 
there  are  two  auricles  and  two  ventricles. 

Each  auricle  communicates  with  a  ventricle,  but  neither  the 
auricles  nor  ventricles  open  into  each  other.  Before  going  into 
the  subject  of  the  circulation  I  must  tell  you  that  the  left 
side  of  the  heart  (left  auricle  and  ventricle)  always  contains 
pure  red  blood,  and  the  right  side  venous  or  impure.  Now, 
having  studied  the  diagram  (fig.  30),  you  can  follow  me  as  1 
trace  the  course  of  the  blood  from  the  heart  through  the  various- 


Lang  Circulation- 


Pulmonary  Artery     .„. 


Pulmonary  Veins. 
Left  Auricle. 


Right  Ventricle 


Aorta. 


Left  Ventricle. 


Fig;.  30. 


Body  Circulation. 


portions  of  the  body  to  the  point  from  which  I  start.  Suppose  the 
blood  just  poured  into  the  left  ventricle ;  this  contracts,*  and  the 
contained  fluid  is  now  expelled— by  a  force-pump  action — into  the 
greatest  of  the  arteries — the  aorta.  Prom  this  it  flows  into  the- 
various  branches,  large  and  small,  until  at  length  it  reaches  the  head, 
brain,  arms,  belly,  legs,  skin,  and  so  forth  ;  thence  it  is  borne  inta 

*  The  whole  chamber  becomes  very  much  smaller  ;  this  is  due  to  the 
shortening  of  the  muscular  fibres,  of  which  it  consists.  It  is  not  a 
mere  india-rubber  lall  action,  but  a  special  phenomenon/characteristic  of 
flesh.  Immediately  after  the  contraction  the  fibres  relax,  and  the  cavity 
is  as  large  as  it  was  before. 


CIRCULATION  OF  THE  BLOOD.  55 

the  capillaries,  and  so  comes  into  contact  with  the  minutest  particles 
of  the  tissues.  Erom  these  it  is  now  re-collected  into  the  veins,  and 
eventually  is  carried  by  the  tw9  venous  vessels— the  upper  and 
lower  vense  cavse  —to  the  right  side  of  the  heart,  and  emptied  into 
the  right  auricle.  This  contracts,  and  the  liquid  mass  is  sent  into  the 
right  ventricle,  which  immediately  contracts  also,  and  the  blood 
being  shut  off  by  the  valve  (Tricuspid,  or  three-toothed  valve) 
behind,  flows  into  a  large  vessel  called  the  pulmonary  artery.  (Vide 
diagram,  fig.  30.)  You  must  not  be  puzzled  to  hear  this  called  an 
artery ;  for,  though  it  contains  impure  blood,  yet,  as  it  carries  blood 
from  the  heart?  it  is  so  named. 

This  artery  is  called  pulmonary,  because  it  bears  the  fluid  to  the 
lung,  the  Latin  name  of  which  is  pulmo.  Well,  then,  the  blood  is 
driven  along  this  canal  to  the  lungs.  Here  it  is  transmitted  to  the 
capillaries  of  these  organs,  exposed  to  the  air  taken  in  as  the  breath, 


Fig.  31. — Upper  surface  of  the  Heart,  the  Auricles  having  been  dissected  away, 
l,  2.  The  Tricuspid  Valve $  3.  The  Mitral  Valve ;  4  and  5.  The  Semilunar  cr  Halt- 
moon  shaped  Valves. 

and  purified  by  absorbing  fresh  oxygen,  and  giving  off  the  foul  air 
or  carbonic  acid.  But  why  does  it  flow  upward  to  the  lung  and  not 
fall  back  upon  the  heart?  Eor  this  reason  :  the  opening  into  the  heart 
is  protected  by  three  half-moon  shaped  (semi-lunar)  valves  (fig.  31), 
which  open  in  the  direction  of  the  lungs,  and  as  soon  as  the  blood 
tries  to  re-flow  into  the  ventricles  these  shut  back,  and  in  this  way 
by  contraction  after  contraction  of  the  heart  the  fluid  is  driven  to  the 
pulmonary  organs.  Having  undergone  exposure  to  the  atmosphere 
and  been  changed  to  pure  blood  in  the  way  I  have  indicated,  it  is 
collected  by  a  number  of  vessels,  which,  by  uniting  with  each  other, 
form  a  single  trunk  that  terminates  in  the  left  auricle.  This  trunk 


56 


POPULAR  PHYSIOLOGY. 


is  named  the  pulmonary  vein, — pulmonary  because  in  connection 
with  the  lung,  and  vein  because  il  conveys  blood  (although  not  of  the 
venous  type)  to  the  heart. 

Prom  this  canal  it  is  gradually  poured  into  the  left  auricle, 
which  now  contracting,  sends  it  into  the  left  ventricle  through 
the  opening  between  the  two.  The  aperture  is  provided  with 
a  pair  of  valves,  that  from  their  resemblance  to  a  bishop's  mitre  have 
been  called  the  mitral  valves  (fig.  32).  These  open  into  the  ventricle, 
thus  admitting  the  blood,  but  when  the  latter  chamber  contracts 
they  close,  or  fall  together,  and  so  the  blood  is  driven  into  the  aorta. 

Again,  the  difficulty  suggests  itself  as  to  its  reflux  into  the 
cavity,  and  again,  I  must  say,  that  here  are  also  three  moon-shaped 
valves,  which  when  the  blood  is  forcibly  driven  into  the  aorta  lie 
tack  against  its  walls  ;  but  when  the  fluid  tries  to  retrace  its  steps, 
shut  down— exactly  like  the  trap-door  in  the  pantomime,  through 
which  harlequin  has  been  rather  forcibly  ejected  —  and  thus 
prevent  its  readmission  into  the  chamber.  The  blood  has  now 
arrived  at  the  starting  point,  and  so  the  circulation  has  been  com- 
pleted. The  action  of  the  heart  is  exactly  that  of  a  pair  of  double 
force-pumps,  as  may  be  seen  by  looking  at  the  diagram  beneath, 


Fig.  32. 

where  (a)  represents  the  right  auricle,  (b)  the  right  ventricle, 
(d)  the  tricuspid  valves,  (<?)  the  semi-lunar  valves  of  the  pulmonary 
artery,  (f)  the  lungs,  (g)  the  pulmonary  vein,  (K)  the  left  auricle, 
(0  the  left  ventricle,  (K)  the  mitral  valve,  and  (/)  the  semi-lunar 
valves  of  the  aorta.  The  pistons  and  cylinders  stand  for  the 
muscular  walls  of  the  different  cavities,  and  explain  their  effect  in 
contracting  on  the  fluid.  The  chambers  of  the  heart  not  only  con- 
tract and  so  diminish  in  bulk,  but  they  afterwards  expand  to  their 
original  size.  By  the  first  process  thev  expel  the  blood  contained  in 
them ;  by  the  second  they  suck  in  the  blood  of  the  adjoining  cavities. 
That  _  they  not  only  contract  but  expand  also  is  proved  by  this  fact, 
that  if  the  heart  when  contracted  be  grasped  in  the  hand,  the  expan- 


USE  OF  THE  ELASTIC  COAT  OF  ARTERIES.  57 

sion,  which  afterwards  ensues,  is  very  perceptible.  The  blood  flows 
in  a  continued  rapid  stream  through  the  arteries,  loses  its  force  in 
the  capillaries,  and  returns  slowly  through  the  veins. 

At  first  one  would  suppose  that  as  the  heart  gives  a  series  of  beats  or 
contractions  one  after  the  other,  so  should  the  blood  be  conveyed 
through  the  arterial  tubes,  in  a  jet-like  manner,  by  a  number  of  jerks  ; 
but  this  is  not  so.  Why  ?  Why  is  it  not  so  in  the  fire-engine,  in  which, 
as  every  one  has  observed,  the  force  is  applied  at  intervals,  by  the  vyork- 
ing  up  and  down  of  the  handles  ?  Because  there  is  a  quantity  of 
compressed  air,  which — being  very  elastic — when  the  force  ceases, 
begins  to  press  on  the  water  and  so  keeps  up  the  flow  till  the  next 
stroke  of  the  handle.  Similarly  in  the  arteries,  save  that  in  these 
the  office  of  the  compressed  air  is  performed  by  their  elastic  sides. 


*  Fig.  32. 


Fig.  32*. — Diagrams  illustrating  the  relative  changes  In  form  of  Auricle  and 
Ventricle.  B.  Auricle  contracting  and  pouring  blood  into  Ventricle ;  /,  the 
Auricle  ;  g,  Ventricle  ;  f,  i,  Mitral  Valves  open  ;  k,  Semilunar  Valves  closed  5  h, 
Aorta,  c.  Ventricle  contracting  and  forcing  Blood  into  Aorta  ;  a,  Auricle ;  b, 
Ventricle  ;  d,  d,  Mitral  Valves  closed;  e,  Semilunar  Valves  open;  c,  Aorta.— The 
arrows  indicate  the  direction  of  the  currents. 

These,  when  the  blood  is  first  driven  into  them,  are  distended,  and  in 
recovering  their  proper  position  press  on  the  fluid  till  the  next  beat 
oi  the  heart,  and  so  on. 

Let  us  now  investigate  the  forces  employed  in  carrying  on 
this  circulation;  for  that  forces  there  are,  is  evident.  If  there 
™ail  fa»stened  to  tn.e  open  end  of  the  aorta  a  tube  containing 
Idlb.  ot  mercury,  this  latter  would  be  supported  by  the  mere  pres- 
sure of  the  blood  against  it.  The  experiment  has  not  been  per- 
lormed  upon  man ;  but  from  the  result  of  similar  experiments  upon 
other  animals  the  deduction  has  been  drawn.  The  action  of  the 
bean,  whose  equivalent  is  13  lb.,  is  certainly  the  most  powerful  ot 
all  the  forces  operating  on  the  blood,  and  is  produced  by  the  mus- 
cular contraction  of  the  left  ventricle. 

When  the  column  of  fluid  is  thus  injected  into  the  arteries 
these  larger  branches,  by  virtue  of  their  elastic  coats,  equalize 
the  flow ;  and  the  smaller  ones,  owing  to  their  being  in  part 
composed  of  muscular  tissue,  contract  upon  the  liquid,  in  this 


58 


POPULAR  PHYSIOLOGY. 


Nerve. 


way  causing  the  continuation  of  the  stream.  At  last,  the  blood 
reaches  the  capillaries,  but  here,  being  divided  into  innumerable 
minute  currents,  and  actual  friction  being  produced,  the  accumu- 
lated force  is  expended,  and  did  not  some  new  power  exert 
itself,  the  circulation  would  come  to  a  stand  still.  The  new  force 
developed  in  this  locality  is  that  of  affinity.  The  tissue  toward 
which  the  blood  is  flowing  requires  certain  elements  contained  in 
the  nutrient  liquid.  These  it  robs  from  the  first  portions  ;  and  those 
behind  having  then  a  greater  attraction  for  the  tissue,  push  the 
plundered  ones  before  them. 

The  injured  victim  is  forsaken  for  one  possessing  the  very  attrac- 
tions that  it  had  formerly  exhibited.  The  diagram  beneath  will 
make  these  remarks  appreciable  (fig.  33). 

The  globular  particles  are  portions  of  blood,  containing  muscle  food 
(»)  and  nerve  fopd(«)j  these  are  drawn  towards  the  muscle  because 

of  an  attraction  between 
the  two.  This  next  de- 
prives them  of  m  \  and 

Muscle,  having  lost  their  attrac- 

tion, they  are  driven  on 
by  the  particles  behind, 
which  have  not  yet  lost 
their  virtue.  In  addition, 
they  are  still  attracted 
towards  the  nerve,  on 
account  of  their  having 

Fig.  33.  the  substance  it  demands, 

and  as  they  are  deprived 

of  this  also,  they  are  again  urged  forward  by  those  in  the  rear.  Just 
as  the  man  subjected  to  the  trying  temptations  of  the  world  loses 
first  one  good  trait  and  then  another,  till  he  eventually  becomes  so 
vitiated  that  either  death  or  reform  must  follow  soon. 

By  a  series  of  alterations,  such  as  I  have  pointed  out,  the  blood 
having  lost  its  nutritious  materials,  and  being  highly  impregnated 
with  the  waste  constituents  of  the  tissues  which  it  lias  taken  in 
exchange,  is  at  length  poured  into  the  smallest  branches  of  the  veins. 
These,  as  I  stated,  are  in  general  provided  with  valves  opening 
toward  the  heart,  and  it  is  of  the  utmost  importance  that  such 
structures  do  exist,  for  the  circulation  of  the  fluid  through  the 
venous  channels  is  dependent  in  a  great  measure  upon  them. 

The  veins  are  usually  close  to  the  surface,  being  placed  between 
the  muscles  and  skin;  and  having  exceedingly  thin  walls,  are 
easily  effected  by  pressure.  Now,  if  we  press  against  &  flexible 
tube  C9ntaining  liquid,  this  must  flow  away  toward  either  end; 
but  if  it  be  prevented  fiWing  in  one  direction,  it  will  certainly 
do  so  in  the  other.  This  is  what  takes  place  in  the  veins— the 
muscles  during  the  ordinary  movements  of  the  body  press  upon 
the  venous  vessels.  The  fluid  contained  in  these  tends  to  flow  in  both 
directions,  up  and  down  ;  but  the  valves  prevent  its  passage  downward 
(fig,  35),  and  therefore  it  ascends,  and  in  doing  so  opens  the  valves  next 


ATTRACTION   OF  TISSUES  TOR  BLOOD. 


59 


in  order,  is  caught  there,  pressed  on  again  and  ascends  in  conse- 
quence ;  and  this  is  continued  till  it  has 
reached  the  main  branches  of  the  system.         <*       ?       e         n 

The  main  trunks  are  two  in  number ;  one 
for  the  superior,  and  the  other  for  the  in- 
ferior division  of  the  body.  These 'have  no 
valves,  and  hence  it  is  necessary  that  some 
compensating  power  be  called  into  play. 
This  we  find  in  the  expansion  or  dilatation 
of  the  heart,  which,  by  a  species  of  suction, 
draws  the  venous  nuid  to  the  right  auricle. 
You  will  perceive  that  we  have  not  yet  com- 
pleted the  circle.  Having  set  out  irom  the 
left  side,  we  have  travelled  round  to  the 
right ;  but  we  must  go  a  few  steps  further. 
The  blood  is  now  sent  by  the  right  ventricle 
to  the  lungs,  passing  on  its  way  thither 
through  the  pulmonary  artery.  Here  the 
vital  fiuid  enters  another  capillary  apparatus 
before  it  returns  to  the  left  auricle  and  ven- 
tricle, and  is  subject  to  the  same  conditions 
as  those  we  saw  when  speaking  of  the 
capillaries  of  the  body  generally.  It  con- 
tains foul  gas  (carbonic  acid),  which  has 
an  attraction  for  the  air  cavities  of  the 
pulmonary  organs.  This  foul  gas  it  now  loses 
—letting  it  escape  in  the  breath— and  then  it  is  pushed  on  by  the 
blood  behind,  as  I  explained  above,  till  at  length  it  arrives  at  the 
left  side  of  the  heart. 

I  am  afraid  you  will  find  the  foregone  remarks  somewhat  dry ;  but  I 
imagine  that  if  they  were  more  extended, 
it  would  be  only  to  intensify  the  puzzle; 
and  unless  I  made  the  description 
longer,  it  would  be  difficult  to  render 
it  clearer. 

We  are  accustomed  to  feel  a  man's 
pulse  in  order  to  ascertain  the  state  of 
his  heart ;  but  I  am  inclined  to  think 
we  do  not  all  understand  the  reason, 
and  that  many  people  believe  that  it  is 
necessary  to  feel  the  wrist  in  par- 
ticular, and  would  no  doubt  ridicule  the 
idea  of  placing  the  hand  on  a  patient's 
neck,  or  his  ankle.  The  pulse  is  simply 
the  effect  produced  on  an  artery  by 
the  force  with  which  the  blood  is  driven 
through  it.  The  vessel  is  elongated — 
stretched  out,  so  to  speak — and  in  con-  Fi  gg  _Vein  ]ai(1  0  en  .  f 

Sequence  lifted  a  little  from  its   bed,  as      end  "nearest  Heart;   v,  Valvej 
shown   in  the  diagram  (fig.  36).      This      a,  aperture  of  smaller  Vein. 


1  2 

Fig.  34.— Diagram  illus 
trating  the  action  of  the 
Valves  of  Veins.  1.  With 
the  valves  open,  to  allow 
of  the  blood  passing  toward 
the  heart;  a,  b,  and  c,  d, 
the  valves;  e,  f,  and  g,  h, 
the  sides  of  the  vessel;  i, 
the  central  channel.  2. 
With  the  valves  closed ;  e,  p, 
and  g,  g,  the  sides  of  the 
vein ,  b,  in,  and  n,  m,  the 
valves. — The  arrows  indi- 
cate the  direction  of  the 
currents. 


60 


POPULAR  PHYSIOLOGY. 


elevation  the  physician  recognises  by  the  pressure  against  the  fore- 
finger, which  he  has  placed  upon  the  skin  over  the  vessel.  The  pul- 
sation, or  pulse,  as  it  is  called,  may  be  felt  in  any  artery,  provided  it 
be  not  too  deeply  situated. 

But  how  does  the  pulse  indicate  the  state  of  the  heart?  It 
•does  so,  as  the  water  from  a  pump  points  to  the  condition  of  this 
latter.  If  the  pump  is  not  being  worked,  there  is  no  flow  from  the 
spout ;  if  the  heart  be  not  acting,  there  is  no  pulse.  If  the  pump  be 
wrought  violently,  the  rapidity  of  the  current  from  the  spout  is  suffi- 
ciently indicative  of  this ;  so,  if  the  heart  be  contracting  rapidly — 
palpitating — the  frequency  of  the  pulsations  points  this  out  also. 

Again,  to  complete  our 

Artery  pulsating.  analogy— If  the   sucker 

of  the  pump  be  in  bad 
repair,  the  water  is  heard 
gurgling  backward,  and 
the  stream  from  the 
spout  is  of  an  irregular 
and  imperfect  character ; 
similarly  in  the  heart,  if 
the  semi-lunar  valves 
Artery  at  rest.  Fig.  36.  are  Disordered,  the  blood 

(by  the  aid  of  the  stetho- 
scope) is  heard  trickling  back  into  the  ventricle,  and  the  pulse  is  faint 
and  of  a  jerking  nature. 

The  beats  of  the  pulse  are  not  so  numerous  in  one  individual  as  in 
another.  Neither  are  they  as  frequent  in  the  aged  as  they  are  in  the 
adult,  nor  in  the  latter  as  they  are  in  children.  Many  circumstances 
affect  the  pulse,  by  acting  on  the  heart  in  the  first  instance.  Of  these, 
muscular  exertion  and  mental  emotion  are  the  most  important.  That 
the  first  influences  the  pulse,  any  one  may  prove  for  himself  in  the 
following  manner.  When  lying  down,  let  him  examine  the  rapidity 
of  his  pulse ;  on  sitting  up  he  will  find  it  about  six  beats  faster,  and 
on  standing  erect  it  will  be  increased  by  an  additional  ten.  Or  let 
him  contrast  the  number  of  pulsations  during  rest  with  that  during 
great  muscular  exercise,  and  the  result  will  satisfy  him.  Excitement 
of  the  mind  accelerates  the  pulse  often  to  an  alarming  extent. 
Which  of  us  has  not  in  some  moment  of  intense  anxiety  felt  the 
heart  thumping  against  the  chest  as  though  it  were  a  coal  hammer  ? 
Feel  the  pulse  of  that  man  on  his  trial  for  murder,  who  is  anxiously 
scrutinizing  the  countenances  of  his  jurymen  as  they  return  into 
court  with  their  verdict !  Lay  your  hand  upon  your  sister's  wrist  as 
the  postman  gives  his  sturdy  summons  on  St.  Valentine's  morning ! 
Confess,  dear  reader,  that  you  yourself  have  at  one  time  had  your 
heart  influenced  by  the  "  grand  passion,"  and  admit,  what  I  want  you 
to  admit — the  control  of  the  mind  oyer  the  organs  of  circulation. 

This  influence  is  so  familiar  to  medical  men  that,  knowing  the  excite- 
ment which  their  presence  in  the  sick-chamber  causes,  they  invariably 
enter  into  a  quiet  conversation  with  the  patient,  in  order  to  restore 
him  to  his  ordinary  state,  before  they  examine  the  pulse.  This  is  not 


FIXATIONS— RAPIDITY  OF  CIRCULATION.  61 

the  only  way  in  which  the  mind  operates  on  the  heart ;  and  occa- 
sionally, instead  of  accelerating  the  pulse,  it  so  affects  the  system  as 
to  paralyze  the  heart  for  a  time.  We  all  know  the_  result  which 
follows  the  communication 'of  some  dreadful  piece  of  intelligence. 
The  heart  ceases  to  perform  its  office,  and  the  individual  falls  as  though 
dead— having  fainted.  It  has  been  said  that  the  heart  is  actually 
ruptured  in  some  cases,  and  Shakespeare,  in  conveying  an  idea  of 
Ceesar's  sense  of  Brutus's  ingratitude,  says—"  Then  burst  his  mighty 
heart."  It  is  said,  also,  that  the  pulse  is  affected  by  the  digestive 
organs,  being  quicker  after  a  meal  than  before  it ;  and  that  it  is  more 
rapid  in  the  morning  than  at  night ;  and  in  the  female  than  the  male. 
The  actual  number  of  pulsations  per  minute  is  as  follows : — 

In  the  infant,  130  to  140  in  the  minute. 
„     adult,     70  to   80 
„     aged,     50  to   65 

The  blood  travels  along  the  arteries  at  the  rate  of  twelve  inches 
per  second,  and  in  the  veins  a  little  slower,  moving  through  only 
eight  inches  in  the  same  period.  The  time  required  for  it  to  traverse 
the  entire  vascular  system  must  not,  however,  be  computed  from 
these  data,  because  a  very  considerable  period  elapses  between  its 
exit  from  the  arteries  and  entrance  into  the  veins  ;  in  other  words, 
whilst  passing  through  the  capillaries.  But  here  chemistry  has  stepped 
in  to  our  aid,  showing  us  that  when  a  salt— which  is  easily  recognised 
by  certain  tests— is  introduced  into  a  vein,  it  is  found  to  travel  the 
entire  circuit  in  the  course  of  half  a  minute,  and  therefore  that  the 
blood  which  conveyed  it  has  also  "gone  its  rounds"  in  thirty 
seconds. 

I  have  now  to  draw  your  attention  to  what  are  termed  the  rhythm 
and  sounds  of  the  heart,  for  these  are  matters  of  the  greatest  import, 
not  only  to  the  physiologist,  but  to  the  physician,  whom  they  enable 
to  judge  of  the  healthy  or  diseased  condition  of  the  propelling  organ. 
By  the  rhythm  we  mean  the  regular  or  systematic  order  observed  by 
the  heart  in  contracting  and  relaxing,  or  dilating.  By  the  sounds  we 
understand  certain  noises,  accompanying  the  contractions,  and  dis- 
coverable by  the  assistance  of  the  stethoscope. 

All  portions  of  the  heart  do  not  contract  at  the  same  time,  but 
as  the  two  sides  of  the  heart  work  independently  of  each  other,  their 
action  is  simultaneous  to  this  extent— while  the 'left  side  is  receiving 
the  pure  blood  and  transmitting  it  to  the  body,  the  right  one  is 
receiving  the  impure  blood,  and  pumping  it  to  the  lungs.  You  can 
at  once  perceive  how  impossible  it  would  be  for  the  two  chambers  of 
one  side  to  contract  together,  when  aware  that  the  fluid  is  sent  from 
one  to  the  other.  The  blood,  let  us  imagine,  has  been  poured  into 
the  two  auricles,  into  the  right  from  the  veins  of  the  system  gene- 
rally, into  the  left  from  the^lungs,  and  then  the  changes  given  below 
take  place. 


POPULAR  PHYSIOLOGY. 


During  a 

fulsation,  which 
shall  divide  in- 
to four  parts  as 
regards  time. 


In  the 


1st 
part. 


2nd 

and 

3rd 

parts. 


4th 
part. 


Right  auricle  contracts,  and 
forces  the  blood  into  the 
right  ventricle, 

and,  at  the  same  time, 
Left  auricle  contracts,  and 
drives  the  blood  into  the 
left  ventricle.  All  these  opera- 

tions are  per- 
Right  ventricle  contracts,  formed  in  the  in- 
and  sends  the  blood  to  the  iterval   between 
lungs,  ( two  beats  of  the 

and,  simultaneously,        pulse  at  the 
Left  ventricle  contracts,  and  \  wrist. 
pours  the  blood  through  the 
arteries  of  the  body. 

A  period  of  apparent  rest, 
during  which  the  auricles 
are  being  filled. 


What  can  be  more  extraordinary  than  the  accuracy  exhibited  by 
this  complex  piece  of  machinery  in  discharging  its  duties,  as  it 
does  incessantly  from  the  cradle  to  the  grave.  Well  may  man 
exclaim,  "  Oh,  Lord !  I  am  fearfully  and  wonderfully  made."  "  How 
manifold  are  Thy  works !  In  wisdom  hast  Thou  made  them  all ;  the 
earth  is  full  of  Thy  riches."  To  those  who  would  find  a  difficulty  in 
supposing  that  all  the  operations  above  described  are  gone  through 
in  so  short  a  period,  I  would  quote  the  words  of  the  illustrious 
Harvey,  who,  in  recounting  these,  observes  that  they  are  not  more 
incredible  than  those  known  to  be  performed  "  in  that  mechanical 
contrivance  which  is  adapted  to  fire-arms,  where,  the  trigger  being 
touched,  down  comes  the  flint,  strikes  against  the  steel,  elicits  a 
spark,  which,  falling  among  the  powder,  it  is  ignited,  upon  which 
the  flame  extends,  enters  the  barrel,  causes  the  explosion,  propels 
the  ball,  and  the  mark  is^ttained ;  all  of  which  incidents,  by  reason 
of  the  celerity  with  which  they  happen,  seem  to  take  place  in  the 
twinkling  of  an  eye."  Now^  for  the  sounds  of  the  heart,  which,  you 
are  aware,  the  doctor  is  listening  to  when  he  places  that  queer 
trumpet-like  instrument  (stethoscope)  against  your  chest. 

"  We  told  her  we  were  trying, 

By  the  gushing  of  her  blood, 
And  the  time  she  took  in  sighing, 
To  see- if  she  were  good." 

They  are,  in  number,  two,— the  first  and  the  second.  The  first  is  a 
sort  of  dull  thumping  sound ;  the  second  more  like  a  short  soft  click, 
which  follows  immediately  after  the  former  one.  Several  words 
have  been  devised  by  different  authors  to  represent  the  relative 


SOUNDS  OF  THE  HEART.  63 

length  and  softness  of  these  sounds, — such  as  lub  dub,  lub  dullup,  &c. 
I  don't  think,  however,  that  they  express  the  impression  produced 
on  the  ear. 

Some  years  since  a  Frenchman,  M.  Groux,  travelled  through 
this  country,  exhibiting  himself  at  medical  schools,  and  excited 
a  good  deal  of  interest  at  the  time.  His  peculiarity  was  this :  the 
breast  bone  was  actually  split  into  two  portions,  and,  by  exercising  the 
muscles  of  his  arms  and  chest,  he  could  separate  these  two,  so 
that  a  triangular  space  was  left,  in  which  the  heart  beat  against  the 
skin  alone,  in  this  way  allowing  the  physician  to  examine  the  circu- 
lating organ  as  if  it  was  folded  in  a  towel.  Some  innocent  folk 
fancied  that  M.  Groux  could  quietly  lay  open  his  chest  and  show  the 
heart  itself,  but  this  was  not  the  case.  In  common  with  hosts  of 
others,  I  had  an  opportunity  of  examining  this  individual,  and,  judg- 
ing from  the  sounds  heard,  it  would  be  difficult  to  find  any  two  words 
which,  by  pronunciation,  would  exactly  resemble  them.  I  think 
that  the  syllables  "  loop-up,"  though  not  accurately  representing  the 
sounds,  will  give  a  fair  notion  of  them ;  loop  being  the  first,  pro- 
longed and  soft  sound ;  and  up  the  second,  short  and  sharp  one. 
You  can  by  a  little  experience  acquire  a  fair  conception  of  these 
sounds  by  placing  your  ear  close  to  the  exposed  chest  of  any  of  your 
friends,  being^  careful  to  put  it  a  little  below  the  left  nipple. 
Another  excellent  method  is  this  :  place  the  fore-finger  of  your  left 
hand,  pointing  upwards,  alongside  your  right  ear,  and  then  tip  it 
gently  at  the  top  with  the  fore-finger  of  the  other  hand,  by  which  a 
very  perfect  imitation  of  the  heart's  sounds  will  be  produced. 

The  cause  of  these  sounds,  you  will  say,  is  obvious  enough.  If  so, 
you  are  wrong ;  at  all  events,  if  it  is  clear  to  you,  it  is  not  so  to 
scientific  men,  who  are  disputing  year  after  year  as  to  the  mode  of 
production.  In  order  to  simplify  the  matter  as  much  as  possible, 
let  us  arrange  in  tabular  form  the  names  of  the  processes  performed 
during  each  sound. 

(The  two  ventricles  contract. 

Dur«  The  point  of  heart  strikes  against  the  chest. 

1st  souiS  ^  The  valves  guarding  the  openings  of  auricles  into  ven- 

LThe  blood  rushes  into  the  aorta  and  pulmonary  artery. 


During, 
Sudsound. 


The  two  sets  of  half-moon-shaped  valves  shut  down  with 


a  click. 


The  two  auricles  contract  and  pour  blood  into  ventricles. 
The*  two  ventricles  expand. 

There  have  been  so  many  questions  raised  as  to  which  and  how 
much  of  these  actions  cause  the  sounds,  that  a  decision  in  the 
present  state  of  science  would  be  impossible.  But  we  may  safely  say 
that  the  ^first  results,  in  a  great  measure,  from  the  impulse  of  the 
heart  against  the  chest,  and  the  shutting  back  of  the  valves  (tricuspid 
and  mitral)  protecting  the  entrances  of  the  ventricles.  Whilst  we  can 
certainly  assert  that  the  second  is  to  some  extent,  if  not  entirely,  pro- 


64  POPULAR  PHYSIOLOGY. 

duced  by  the  flapping  back  of  the  half-moon-shaped  valves  of  the 
aorta  and  pulmonary  artery.  In  proof  of  this,  a  most  interesting 
experiment  was  tried  in  Dublin  in  the  year  1834,  when  the  British 
Association  met  in  that  city.  A  needle,  barbed  at  its  end,  was 
thrust  into  the  aorta  of  a  donkey,  and  the  valves,  being  caught  by  it, 
and  hooked  back,  it  was  observed  that  the  second  sound  had 
almost  completely  vanished,  not  being  detected  when  sought  for  witli 
the  stethoscope.  Afterwards,  when  the  needle  was  removed,  and 
the  parts  restored  to  their  proper  positions,  the  second  sound  was 
detected  nearly  as  usual. 

If  you  have  had  the  patience  to  wade  through  the  above  account, 
you  are  prepared  to  recognize  the  immense  value  of  a  knowledge 
of  physiology  to  the  physician.  The  slightest  alteration  of  the 
natural  sounds  informs  him  that  something  is  going  wrong,  and  his 
knowledge  of  the  cause  of  each  enables  him  to  conclude  as  to  what 
particular  locality  is  deranged,  which  his  acquaintance  with  practical 
physic  may  then  give  him  the  power  of  repairing.  In  no  case  could 
a  medical  man,  ignorant  of  physiology,  hope  to  produce  the  cure  of 
a  diseased  heart,  except  by  the  merest  chance.  As  well  might  one 
entirety  unacquainted  with  the  mechanism  of  a  watch  expect  to 
repair  it  when  injured,  by  poking  first  at  this  wheel,  and  then  at 
that  •  and  in  both  cases  the  result  would  be  pretty  nearly  the  same, — 
absolute  destruction  of  parts  hitherto  in  order,  and  no  improvement 
whatever  in  those  which  nad  been  before  diseased. 

It  may  be  of  interest  to  you  to  know  that  some  years  since  a 
gentleman— Colonel  Townsend,  lived,  who  possessed  the  power  of 
controlling  the  actions  of  his  heart  and  lungs.  You  will  tell  me  this 
is  quite  simple— you  can  do  it  yourself.  Not  so  fast.  It  is  quite  im- 
possible, at  all  events  improbable,  that  you  have  any  such  ability. 
Draw  in  your  breath,  now,  and  you  are,  bloated  like  the  frog  in 
the  fable,  undergoing  your  torture  with  heroic  fortitude.  The  gallant 
gentleman  I  have  mentioned,  however,  could  really  influence  hi& 
heart  much  in  the  same  way  as  you  can  control  the  action  of  your 
fore-finger,  which  I  fancy  I  see  elevated  in  an  attitude  of  scepticism ; 
as  the  Ingoldsby  legend  goes  :— 

"  The  sacristan,  he  says  no  word,  to  indicate  a  doubt, 
But  "he  puts  his  thumb  unto  his  nose,  and  draws  his  fingers  out." 

Colonel  Townsend  performed  the  experiment  once  in  the  presence  of 
his  physician,  who  cautioned  him  strongly  against  its  repetition. 
Nevertheless,  he  did  again  exhibit  the  control  he  had  over  his  cir- 
culatory organs,  and  this  time  more  triumphantly  than  ever,  for  he  so 
completely  suppressed  the  heart's  action,  that  it  never  throbbed 
again.  The  unlucky  individual  added  another  name  to  the  list  of 
scientific  martyrs  which  I  hinted  at  in  a  previous  chapter. 

It  would  not  be  unfair  to  say,  "Prove  this  circulation  you  have  been 
talking  so  much  about."  I  shall  imagine  that  the  mandate  has 
gone  forth,  and  having  stated  my  case,  that  I  am  bound  in  support 
of  it  to  produce  my  witnesses ;  or,  as  the  lawyers  say,  "  go  into- 
evidence." 


EVIDENCE  IN   SUPPORT  OF  THE   CIRCULATION. 


65 


\:tery. 


Q.  Your  name,  sir,  is  Anthropotomist*  ? — A.  Yes.  Q.  Having 
examined  the  veins  of  the  body,  you  have  found  certain  struc- 
tures termed  valves  ? — A.  I  have.  Q.  What  do  you  consider  to 
be  the  office  of  these  valves  ?  (Court  objects  to  this  question,  as  the 
subject  is  not  one  upon  which  an  opinion  is  sought.)  Are  these 
valves  so  situated  that  the  blood  in  the  veins  can  now  freely  in  both 
directions? — A.  Most  certainly  not.  Q.  In  what  direction  can  the 
fluid  travel  ?—A.  Only  toward  the  heart.  Q.  Explain  this  matter 
to  the  jury?— A.  If  I  took  a  vein,  that  travelling  from  the  hand  to 
the  shoulder,  for  example,  and  by  means  of  a  syringe  tried  to  force 
water  from  the  shoulder  end  to  the  hand,  I  could  not  do  so  on  account 
of  the  valves ;  but  I  could  force  the  fluid  from  the  hand  toward 
the  shoulder  without  any  difficulty.  Q.  If  an  artery  and  vein  be 
wounded,  is  there  any  difference  as 
regards  the  end  of  each  from  which 
the  blood  is  poured  ?—A.  There  is. 
In  the  artery  it  always  flows  from 
the  cut  end  nearest  the  heart,  in 
the  vein  from  the  open  extremity 
furthest  from  the  heart.  Q.  I  am, 
then,  to  understand  that  arteries  Artery 
are  always  carrying  blood  from  the 
heart  and  veins  to  it  ? — A.  Yes.  0. 
But  if  this  continues  all  through 
life,  it  is  evident  that  the  blood.  Veir 
ever  flowing  from  the  hand  toward 
the  heart,  must  be  brought  there 
by  the  arteries?  —  A.  Quite  so. 
Q.  Can  you  prove  that  a  commu- 
nication actually  exists  ? — A.  Yes. 
If  I  place  the  foot  of  a  live  frog 
under  the  microscope,  and  observe 
it,  I  shall  perceive  that  the  arteries 
terminate  in  minute  channels — the 
capillaries— which  end  on  the  other 

side  in  the  veins,  and  I  shall  observe  the  blood  passing  through 
these  channels  into  the  venous  system.  (Fig.  37).  Q.  The  main 
artery,  from  which  the  other  arteries  are  derived,  arises  from 
the  left  side  of  the  heart  ? — A.  Yes.  Q.  And  the  great  veins,  which 
the  smaller  ones  terminate  in,  open  into  the  right  side  of  the 
heart  ?—A.  Exactly  so.  Q.  But  there  is  no  communication  between 
the  two  sides  ?— A.  No.  Q.  How;  then,  can  the  blood  form  a  circle  ? 
— A.  I  shall  explain.  From  the  right  ventricle  there  springs  a  vessel 
into  which  the  venous  fluid  must  be  poured  by  the  contractions  of  that 
chamber,  and  through  which  the  blood  impure  in  nature  is  forwarded 
to  the  lungs.  From  these,  when  cleansed,  it  is,  by  a  special  vessel, 
returned  to  the  left  side  of  the  heart ;  and  this  I  can  show  in  the  lung 
of  the  frog,  in  which  the  fluid  may  be  seen  coursing  from  and  returning 


From  two  Greek  words  signifying  "a  man"  (mortal),  and  "to  cut." 


G6  POPULAR  PHYSIOLOGY! 

to  the  circulatory  organ.  (Cross-examination  being  declined,  the 
witness  has  left  the  box.) 

"  My  lord  and  gentlemen  of  the  jury : — in  this  case  I  am 
counsel  for  my  client  Physiologist,  and  1  shall  endeavour,  whilst 
speaking  to  the  evidence  which  has  just  been  elicited,  to  deal 
with  the  subject  as  briefly,  but  withal  as  clearly,  as  the  circum- 
stances will  permit  me.  It  is  my  intention  to  show  you  (as  my 
learned  friend  observed  in  opening  the  case),  that  a  certain  individual, 
one  Sanguis  by  surname,  has  been  during  a  considerable  period  of 
time — viz.,  the  life-time  of  his  master,  Homo,  in  the  habit  of  travelling 
in  a  peculiarly  circuitous  manner  along  sundry  canals  (blood-vessels), 
from  and  to  a  certain  metropolis— the  heart.  That  the  routes  he  has 
pursued  in  going  and  returning  have  not  been  identical ;  but  that,  on 
the  contrary,  he  has  invariably  set  out  by  one  series  of  canals— the 
arteries — and  come  home  by  a  second  and  distinct  water  line— the 
veins.  That  you,  gentlemen,  may  now  accurately  conceive  the  course 
followed  by  this  sanguinary  character,  I  beg  to  refer  you  to  the 
diagrams  and  schematic  representations  (Figs.  29,  30,  31)  already  laid 
before  you  by  my  client. 

"  You  are  now  prepared  to  follow  me  as  I  move  forward  step 
by  step  through  the  complex  chain  of  circumstantial  evidence 
given  by  the  distinguished  man  of  science  you  have  had  before  you. 
You  observe  in  the  delineations  of  the  metropolis  I  have  alluded  to, 
it  is  distinctly  shown  that  the  two  portions  have  no  direct  communi- 
cation with  each  other ;  that  certain  canals  lead  from  the  left  side  to 
the  various  regions  around,  and  that  these  canals  then  are  continuous 
with  others  which  return  to  the  right  side — the  first  being  called 
arteries,  the  second  veins;  and,  finally,  that  adjacent  to  this  metro- 
polis is  a  great  tract,  known  by  the  name  of  Lung,  to  which  a  canal 
passes  from  the  right  wing  of  the  metropolis,  and//o^  which  a  similar 
canal  returns  to  the  left  wing. 

"  Now,  it  is  admitted  that  the  prisoner  was  seen  in  the  lung,  in 
both  wings  of  the  metropolis,  in  the  various  regions  lying  round, 
and  in  both  the  arterial  and  venous  canals ;  from  which  we  conclude 
that  he  has  travelled  in  a  circle.  He  alleges,  in  defence,  that  he 
has  never  adopted  a  circuitous  route,  but  has  journeyed  from 
the  heart  to  the  surrounding  country,  and  also  from  the  right  side 
of  the  heart  through  the  veins  to  the  same  localities,  constantly 
going  and  returning  by  the  same  canal.  To  this,  gentlemen,  I  can 
only  say,  recall  the  statements,  the  reliable  statements  of  Anthro- 
pptomist.  That  gentleman  informed  you  'that  a  system  of  turn- 
pikes existed  along  the  venous  canals  _  at  which  passengers  ^  were 
refused  passage  in  any  but  a  homeward  direction ;  also,  that  owing  to 
the  existence  in  the  arteries  of  a  very  powerful  current  in  the  outward 
line,  it  would  be  impossible  for  any  individual  to  return  by  those 
canals  ;  and  finally,  that  the  only  communication  between  the  right 
and  left  districts  of  the  metropolis  was  via  the  lungs.'  Recall,  I 
repeat,  those  statements,  and  I  believe  that  as  conscientious  and 
sensible  men,  viewing  the  matter  in  the  most  impartial  and  unbiassed 
manner,  you  will  feel  bound  to  bring  in  a  verdict  for  my  client. 


THE  BAEBER-SURGEOXS.  67 

For  Sanguis  has  been  seen  in  both  districts  of  the  heart,  in  the 
lungs,  arteries,  and  veins ;  and  the  only  mode  by  which  he  could 
consecutively  have  presented  himself  in  these  different  localities  is  by 
performing  the  circuitous  journey  I  have  contended  for." 

A  wonder  it  seems,  that  the  old  barber-surgeons  of  England,  who 
from  their  practice  of  phlebotomy  must  have  been  well  acquainted 
with  the  difference  of  direction  observable  in  the  flow  of  blood 
through  arteries  and  veins,  never  hit  upon  the  cause,  never  even  for 
a  moment  lighted  upon  the  real  object  of  this  distinction.  For  be  it 
known  to  you,  dear  reader,  that  the  barber-surgeons  of  this  country 
were  once  a  much  more  respectable  body  of  men  than  they  are  in  our 
days.  And  when  I  say  in  our  days,  I  say  it  advisedly,  because  the 
barber-surgeons,  though  nearly  extinct  in  Great  Britain,  are  still 
represented  by  a  few  antique  specimens,  who  practise  the  arts  of 
blood-letting  and  shaving  in  certain  remote  localities. 

Why,  you  will  ask,  should  these  professors  of  the  ars  medendi  have 
struck  at  the  root  of  this  9bscurity  ?  Because,  from  their  practice  of 
bleeding,  they  were  familiar  with  the  necessity  of  putting  a  bandage 
on  the  arm  before  opening  the  vein,  in  order  that  no  air  should  be 
sucked  or  drawn  into  the  end  nearest  the  heart,  as  soon  as  the  vessel 
had  been  divided,  and  because  they  knew  very  well  that  prior  to  the 
application  of  the  lancet,  when  the  bandage  had  been  on  for  a  short 
time,  the  artery  was  swollen  above  it,  and  the  vein  below.  The  fellows, 
it  is  thought,  though  shavers,  were  not  otherwise  observant;  and  from 
having  been  brought  up  in  a  state  of  barberism,  much  allowance  must 
be  made  for  their  want  of  progress. 

Are  there  many  who  know  the  meaning  of  the  barber's  sign  which 
projects  boom-fashion  from  the  windows  of  some  of  the  perfumers  of 
"the  great  unwashed?"— a  long  pole  some  nine  feet  in  length,  of  a 
red  colour,  with  a  white  band  twining  around  it  from  end  to  end. 
This  is  its  signification,  and  one  that  I  fear  many  of  the  proprietors 
are  unaware  of :  the  scarlet  rod  is  intended  to  convey  a  notion  of 
blood,  and  the  white  stripe  which  winds  around  it  of  the  bandage  em- 
ployed in  the  operation  of  blood-letting. 

-  That  the  surgical  practice  of  these  reputable  members  of  our  pro- 
fession was  not  confined  to  the  mere  abstraction  of  the  vital  fluid  is 
shown  by  the  "Diary  of  Samuel  Pepys,"  where  the  eccentric  author 
mentions  having  broken  his  head  whilst  returning  from  some  of  his  not 
unfrequent  symposia,  and  having  had  it  repaired  by  a  barber-surgeon, 
for  which  he  "  did  pay  "  five  shillings.  Here  I  am  reminded  of  the 
fact  that,  in  the  present  day,  our  "general  practitioners"  have 
only  to  undertake  the  charge  of  the  public  hair  and  whiskers,  and 
they  will  then  pursue  an  avocation  whose  duties  are  vastly  more 
multifarious  than  those  of  their  respected  prototypes ;  inasmuch  as 
they  will  engage  to  shave  you,  bleed  you,  mix  your  physic,  and  cut 
your  hair,  "all  for  the  small  charge  of  two  and  sixpence." 

In  Germany  the  barber  still  fills  the  office  of  phlerjotomist — indeed, 
this  is  as  much  a  portion  of  his  trade  as  the  employment  of  the  shears ; 


G8  POPULAR  PHYSIOLOGY. 

and  the  sign  above  his  establishment  is  a  series  of  brightly  polished 
brass  plates  suspended  from  a  horizontal  bar,  and  swinging  to  and  fro 
by  the  action  or  the  wind.  The  plates  are  significant  of  the  circum- 
stance, that  the  blood,  on  flowing  from  the  vein,  is  usually  received  in 
a  dish  or  some  such  utensil. 

1  recollect  not  long  ago,  being  in  a  German  theatre,  witnessing 
the  performance  of  one  of  those  burlesques,  of  which  the  Germans 
are  so  fond,  when  suddenly  my  ears  were  startled  by  a  shrill  scream, 
arising  from  the  pit  (sitz  parterre).  On  looking  down,  immense 
confusion  appeared  to  have  seized  upon  the  people  below,  which 
seemed  to  have  been  caught  up  by  the  dramatis  persona;  for 
in  less  time  than  it  has  taken  you  to  read  this  description,  the 
curtain  dropped.  Anxious  to  discover  the  origin  of  all  this  dis- 
turbance I  descended  to  the  pit,  and  found  that  during  the  per- 
formance a  man  had  been  attacked  by  apoplexy;  his  wife,  seeing 
him  fall  in  a  state  of  insensibility,  had  shrieked  out,  and  ere 
the  curtain  had  fallen  a  prompt  and  energetic  barber,  who  had  been 
sitting  a  few  seats  in  the  rear,  had  opened  a  vein  upon  the  spot,  and 
was  now  having  the  patient  conveyed  to  another  locality.  Obstupui. 
Comas  did  not  steturunt,  but  vox  faucibus  haesit— which  freely  trans- 
lated means,  I  was  dumb-foundered,  to  think  that  almost  in  the 
twinkling  of  an  eye  so  many,  things  had  happened.  1  returned  to 
my  box  seriously  impressed  with  the  belief  that  a  corps  of  German 
barber-surgeons  might  be  imported  into  the  country  districts  of 
England  with  advantage. 

Who  discovered  the  circulation  of  the  blood  ?  A  very  nasty  tick- 
lish question,  and  one  not  easily  replied  to.  In  this  age  of  perverse- 
ness  and  aping  after  originality,  it  is  often  endeavoured  to  earn  a 
name  by  writing  a  work  to  blacken  a  character  heretofore  without 
blemish,  or  canonize  some  wretch  whom  two  centuries  of  society 
have  condemned.  This  habit  has  not  been  foreign  to  physiological 
writers,  and,  therefore,  the  ques^n  as  to  priority  of  discovery, 
not  only  in  the  case  of  the  circulation,  but  in  many  other  instances 
also,  is  a  vexed  one.  If  I  were  sworn  to  state  my  opinion  regarding 
the  discovery  of  the  circulation,  I  should  say :  on  the  one  hand, 
Harvey  does  not  merit  all  the  credit  he  has  received ;  on  the  other, 
the  circulation  was  not  proved  before  his  investigations,  whilst,  in  any 
case,  he  did  not  give  all  the  details. 

Galen,  who  lived  AD.  150,  was  the  first  to  form  any  true  idea 
concerning  the  process,  for  lie  asserted  that  the  arteries  carried 
blood,  and  not  air.  Vesalius  was  the  next  in  the  field,  and  showed 
(about  the  middle  of  the  sixteenth  century)  that  no  direct  com- 
munication existed  between  the  right  and  left  sides  of  the  heart. 
He  was  a  most  enthusiastic  and  philosophic  investigator,  and  suf- 
fered under  the  religious  prejudices  of  the  period;  for,  not  contenting 
himself  with  the  examination  of  the  bodies  of  the  lower  animals,  he, 
on  one  occasion,  made,  as  he  thought,  a  "post-mortem"  examination 
of  the  body  of  a  young  nobleman.  Judge  of  his  horror  and 
astonishment  on  finding,  when  the  chest  was  opened,  that  the  heart 
was  still  beating.  This  became  noised  abroad,  and  he,  poor  mao, 


HISTORY  OF  DISCOVERY  OF  CIRCULATION.  G9 

was  obliged  in  penance  to  undertake  a  mission  to  the  Holy  Land,  and 
afterwards  fell  into  disgrace  and  temporary  oblivion. 

The  next  labourer  was  Servetus,  who,  with  tolerable  distinctness 
pointed  out  that  the  blood  was  carried/row  the  heart  to  the  lungs,  and 
then  returned ;  but  he  also  came  to  an  untimely  end.  He  was  a  divine ; 
and,  indeed,  published  this  physiological  discovery  in  a  theological  work ; 
and,  to  quote  the  words  of  Mr.  L&wes,  "  both  he  and  his  treatise  were 
roasted  by  Calvin."  A  few  years  subsequently,  Ceesalpinus,  a  distin- 
guished botanist,  first  coined  the  expression,  "circulation  of  the  blood," 
and  described  the  circulation  thus  :  "  In  animals  we  perceive  the  food 

brought    by  the  veins  to  the  heart, and  it  is  distributed 

over  the  entire  body  by  the  arteries"  Next,  we  observe  that,  in 
1574,  Harvey's  own  master,  Fabricius,  discovered  the  valves  in  the 
veins.  Finally,  in  1619,  we  find  Harvey  himself  appearing  in  the 
arena.  It  is  quite  certain  that  much  had  been  done  for  him.  Thus  : — 

1st.  It  had  been  proved  (?)  that  the  arteries  carried  the  blood  to 

the  body. 
2nd.  That  there  was  no  communication  between  the  two  sides  of 

the  heart. 
3rd.  That  the  blood  was  sent  from  the  heart  to  the  lungs,  and 

returned  to  the  former. 

4th.  That  the  food  was  brought  by  veins  to  the  heart ;  and— 
5th.  The  term  "circulation  of  the  blood"  had  been  employed. 

But  still,  all  the  information  was  in  crude  form,  and  no  decided  con- 
ception of  the  entire  course  of  the  blood  existed.  All  these  defici- 
ences  he  supplied,  and  to  him  all  the  merit  of  establishing  the 
"circulation"  is  due. 

Harvey,  however,  was  unaware  of  the  manner  in  which  the  fluid 
passed  from  arteries  into  veins,  and  this  hiatus  remained  unfilled  till  the 
discovery  of  the  capillaries  by  Malpighi,  in  1661— a  discovery  which 
completed  the  matter,  and  which  is  a  proof  of  the  immense  advan- 
tages accruing  to  physiology  from  the  use  of  the  microscope. 


70  POPULAR  PHYSIOLOGY. 


CHAPTER  VIII. 

Kespiration — What  we  mean  by  Drowning — The  Chest — Lungs— Air 
Vesicles — Suction — How  the  Air  is  introduced  into  the  Air  Cells — 
Enlargement  of  the  Cavity  of  the  Chest — Ascent  of  Eibs,  Descent  of 
Diaphragm — Ordinary  Respiration — Elasticity  of  the  Lungs — Resist- 
ance to  be  overcome  in  Inspiration — Effect  of  a  Gun-shot  Wound  in  the 
Chest — Law  of  Mutual  Diffusion  of  Gases — Intermixture  of  Hydrogen, 
Gas  and  Carbonic  Acid — Capacity  of  the  Lungs — Spirometers— What 
we  inhale  and  exhale — Experiment — Is  Carbonic  Acid  generated  in 
the  Lungs  ?  —  Experiments  on  Birds  —  Composition  of  the  Air  — 
Poisonous  Action  of  Carbonic  Acid— Importance  of  an  attention  to  the 
Principles  of  Hygiene  —  Why  we  breathe  —  Organ  of  Voice  —  The 
Larynx — The  Vocal  Chords — Action  of  these  latter  —  Use  of  Epi- 
glottis— Voice  of  celebrated  Singers — Speech  —  Stammering— Ven- 
triloquism — Whistling  —  Sighing  —  Yawning — Sneezing— Laughing— 
Consumption  and  Bronchitis. 

A  MAX  tumbles  into  the  river,  and  you  say  lie's  drowned.  What 
do  you  mean  ?  Why,  that  he  is  suffocated— asphyxiated — you  know. 
Ah,  dear  reader,  you  cannot  thrust  those  long  words  dovyn  my  throat. 
Confess  your  ignorance,  and  say  that  all  you  know  is  that  he  is 
drowned.  His  breathing  ceased  because  he  had  not  air ;  his  blood, 
not  being  purified,  would  not  pass  to  the  left  side  of  the  heart ;  and 
so  the  circulation  was  arrested,  and,  in  consequence,  life  itself.  Now 
the  solution  of  all  the  questions  involved  in  these  processes  is  only  to 
be  arrived  at  by  the  study  of  the  function  of  respiration.  This  study 
we  shall  pursue  in  the  same  way  as  \ye  followed  that  of  digestion  and 
circulation ;  viz.,  we  shall  first  examine  the  machine  ;  next,  show  how 
it  works ;  and  lastly,  treat  of  the  advantage  of  this  labour. 

The  organs  engaged  in  respiration  are,  the  lungs,  windpipe,  and 
chest.  The  lungs,  or  lights  as  they  are  called  by  butcliers,are  two  large, 
spongy  masses,  which,  during  life,  fill  the  whole  cavity  of  the  chest, 
just  allowing  the  heart  and  great  blood  vessels  to  rest  between  them, 
and  the  gullet  to  pass  down  at  the  rear  (vide  fig.  38).  They  are  enclosed 
in  two  membranous  sacs,  and  though  enclosed  are  yet  outside  them. 
You'll  say  this  is  a  paradox ;  how  can  they  be  outside  and  in  ?  Have 
you  ever  seen  one  of  those  glasses  with  hollow  sides,  partly  filled  with 
some  coloured  liquid  resembling  porter,  and  which  amuse  children 
exceedingly,  from  its  being  impossible  to  spill  the  supposed  contents  ? 
If  you  have,  you  can  understand  how,  if  you  pour  water  into  a  glass 
of  that  kind,  it  will  virtually  be  in  it  and 'yet  not  in  it.  Or,  suppose 
your  own  head  buried  in  a  double  nightcap  ;  here,  as  you  know,  your 
head  is  in  the  cap  and  yet  not  within  it.  Well  then,  in  the  same  way 
do  the  lungs  lie  in  their  membranous  bags.  The  real  interior  of 
these  is  unceasingly  being  oiled  by  a  peculiar  secretion,  so  that  in 
this  manner  the  two  surfaces,  though  constantly  rubbing  against 


STRUCTURE  OF  LUNGS.  71 

each  other,  sustain  no  injury,  owing  to  the  friction  being  provided 
against  by  the  oiled  surfaces.  These  sacs  are  termed  pleurae*  and 
when  by  any  cause  their  lubricating  power  ceases,  the  rubbing  of  the 
rough  sides  causes  intense  agony  in  drawing  the  breath,  in  fact,  the- 
bags  are  diseased,  and  the  malady  is  named  pleuritis,  or  in  common 
parlance,  pleurisy. 

The  lungs  consist,  like  other  glands,  of  a  canal  system  (fig.  39,  #,  6,  c, 
e\  by  which  their  secretion  (carbonic  acid)  is  carried  out,  and  a  quantity 
of  vesicles,  by  which  it  is 
separated  from  the  blood. 
The  tubes  which  convey 
from  the  lungs  the  foul  air 
and  vapour  (which  are  their 
secretions)  commence  at 
the  windpipe.  This,  in  its 
turn,  begins  at  the  larynx 
(that  group  of  structures  of 
which  the  Adam's  apple  is 
one),  and,  after  descending 
into  the  chest,  divides  into 
two  smaller  conduits — the 
bronchial  tubes  —  which 
again  divide  into  two  lesser 
ones,  and  so  forth;  this 
process  of  division  and 
subdivision  being  carried 
on  till  eventually  an  arbore- 
scent collection  results, 
whose  final  branches  are 
microscopically  minute.  If 
we  examine  the  furthest 
end  of  one  of  these  lungs 
we  shall  perceive  that  it  is 
connected  with  an  irregular  _.o ,  ,  r 

labyrinth  Of  Cavities,  which  and  front  of  the  ribs  having  been  removed.  The 
it;  rnmprl  n  InVmlp  IVnw  lungs  have  been  inflated,  and  the  windpipe  has 

is  named  a  10   ue.     rjow  bee*  tied      the  h        b  and    the  lu^s 
tins  lobule  is  a  portion  ot  a  large  gland.   The  other  letters  refer  to  parts 

the    vesicular    part    of  the    seated  in  the  neck. 

lung,  and  is  composed  of  an 

immense  number  (18,000)  of  cells,  about  the  150th  of  an  inch  wide. 
These  communicate  very  freely  with  each  other,  are  bounded  by  a 
delicate  transparent  web,  and  have,  lying  between  them,  thousands  of 
exquisitely  slender  capillary  blood-vessels.  It  has  been  computed 
that  of  these  air  cells  there  are  in  the  human  lungs  not  less  than  six 
hundred  millions— &  fact  well  calculated  to  impress  upon  us  the  vast 
importance  of  the  pulmonary  organs. 

You  have  already  appreciated,  the  relation  of  these  different  parts. 
The  air  cells  are  in  clusters,  those  "of  each  group  or  lobule  being  con- 

*  From  the  Greek  for  lung. 


Fig.  38.— Chest  of  a  Child,  the  heart,  bone, 


72  POPULAR  PHYSIOLOGY. 

tinuous  with  each  other.  To  each  cluster  is  attached  the  ultimate 
branch  of  a  bronchial  tube,  which,  as  it  travels  upwards,  unites  with 
a  others,  until  at  last,  through  the 

windpipe,  a  communication  is  esta- 
blished "between  the  atmospheric  air, 
externally,  and  the  minute  congeries 
of  air  cells  within.  The  fine  blood- 
vessels are  situate  between  the  cells, 
being,  as  it  were,  packed  along  with 
them,  so  that  each  capillary  tube  has 
an  air  cell  on  both  its  sides. 

The  larger  bronchial  tubes  are 
lined  on  the  inside  by  a  beautiful 
delicate  down,  soft  as  velvet,  of 
which  I  have  just  placed  a  portion 
under  the  microscope ;  and  what  a 
pretty  sight  is  presented— a  field  of 
corn  in  miniature !  This  down  is 
formed  by  an  almost  infinite  number 
of  extremely  minute,  hair-like  fila- 
ments, resting  on  club-shaped  pro- 
jections, and  perpetually  moving  in 
one  direction,  giving  exactly  that 
appearance  to  the  eye  which  is  pro- 
duced by  a  meadow  swayed  in  gentle 
undulating  curves  by  the  action  of 
the  wind  (vide  fig.  40).  I  now  drop 
a  small  quantity  of  a  solution  of  potash 
upon  the  specimen,  and  I  have  a 
"  dissolving  view"  produced,  for  the 
elegant  little  filaments  (cilia)  have 
vanished. 

Surely,  Ihese  exquisite  organisms 
There  must  be  some  office  which 


Fig.  3Q.— Lungs  and  Windpipe  of 
Man.  On  the  right  side  the  soft 
tissue  has  been  dissected  away, 
and  the  tubes  alone  are  seen,  a, 
the  larynx ;  b,  the  windpipe  ;  c  and 
e,  large  and  small  bronchial  tubes ; 
d,  the  left  lung. 


are  not  without 
they  fulfil. 


a  purpose? 


"  Oh,  happy  living  things  !     No  tongue 

Their  beauty  might  declare  : 
A  spring  of  love  gushed  from  my  heart, 
And  I  blessed  them  unaware." 

The  cilia  always  move  in  one  direction,  and  in  the  bronchial  tubes  this 
is  toward  the  windpipe— upwards.  Hence  all  particles  of  dust,  all 
sorts  of  materials  in  a  finely  powdered  state,  which  may  be  accident- 
ally sucked  in  during  respiration,  are  prevented  descending  into  and 
accumulating  in  the  air  cells  by  the  influence  of  these  cilia.  A  small, 
almost  atomic,  portion  of  road  dust  we  often  draw  into  .the  lungs  on 
a  blustry  summer's  day,  but  it  effects  no  injury,  for  it  hardly  has  got 
in  before  the  cilia  "  take  it  in  hand,"  and  it  is  sent  back  again  from 
one  to  the  other  till  it  has  reached  the  mouth. 
Were  it  not  for  this  grand  provision,  all  the  millers  and  stone 


CILIA  AND  MUSCLES  OF  LUXG.  73 

cutters  would  be  exterminated  in  a  very  short  period.  Even  as 
it  is,  they  do  meet  their  death  sooner  than  other  folk,  because 
of  the  inability  of  the  cilia  to  prevent  all  the  particles  entering. 
A  more  energetic  atom  than  usual  will  elude  their  vigilance  and 
slip  down  occasionally,  and  this  being  oft  repeated,  the  collected 
matter  sets  inflammation  and  other  morbid  processes  agoing,  which 
end  in  the  extinction  of  life.  The  bronchial  tubes  and  windpipe 
are  composed  of  a  kind  of  gristle  or  cartilage,  mixed  with  tissue 
of  a  sinewy  description ;  and  in  addition  to  these  there  are  a  few 
fibres  of  muscular  tissue  (flesh).  These  muscular  filaments  can 
hardly  be  seen,  but  a  very  ingenious  experiment  has  shown  us 
their  existence.  Muscle  always  contracts  when  galvanized,  and 
therefore  if  a  galvanic  shock  causes  the  lung  tissue  to  contract,  it 
probably  contains  muscle.  An  English  physiologist  having  dissected 
out  the  lung  and 
bronchial  tubes  of 
an  animal,  placed 
the  entire  organ  so 
that  the  opening  of 
the  \yindpipe  was 
opposite  the  flame 
of  a  candle;  next 
he  applied  the  wires 
of  the  galvanic  bat- 

fprvtnthp  Inner  anrl         Fig.  40.— A  portion  of  the  Tiling;  membrane  of  the 
0  ine  iun=,  an  I     Windpipe>  showing.  the  Ci'ia.     «,  the  club-shaped  cells  ; 
lie  Heard  tlie  air  rush.     bi  partJCles  of  matter ;  c,  the  Cilia.— The  arrows  indicate 
Out,    and     Saw    the     the  direction  of  the  currents, 
candle  extinguished.  _ 

Tin's  information  is  of  great  value,  for  it  shows  us  the  cause  of 
what  many  people  have  experienced— spasmodic  asthma.  In  this 
disease  the  chief  symptom  is  a  feeling  of  sudden  suffocation,  and  this 
is  produced  by  the  contraction  of  some  muscular  bands  sur- 
rounding the  smaller  bronchial  tubes,  thus  closing  the  channel 
and  preventing  the  passage  of  air  to  the  cells.  Now,  it  has 
been  found  experimentally  that  such  substances  as  thorn-apple 
and  deadly  nightshade  prevent,  to  a  great  extent,  these  contractions, 
and  therefore  we  employ  both  these  remedies  to  alleviate  the 
unpleasant  sensations.  I  merely  mention  these  facts  to  show  you 
how  we  obtain  a  knowledge  of  the  cause  of  a  disease  through 
the  assistance  of  physiology,  and  that  when  we  wish  to  discover 
a  remedy,  we  must  also  appeal  to  the  same  branch  of  learning. 

The  lungs  then,  as  you  now  understand,  are  a  pair  of  spongy  sacs, 
divided  internally  into  millions  of  little  compartments,  which  the 
air  reaches  after  its  journey  through  all  the  bronchial  tubes. 

The  next  points  are,  how  we  bring  the  fresh  air  in,  and  force  the  foul 
air  out.  These  we  can  only  solve  by  a  reference  to  the  mechanism  of 
the  chest.  The  latter  is,  as  I  before  said,  a  boney  cage,  but  though  a 
cage,  the  air  cannot  enter  it  though  the  framework.  (See  fig.  41.) 
The  component  wires  having  their  intervening  spaces  filled  up  by 
flesh,  and  the  floor  being  formed  by  a  large  dome-shaped  muscle, 


74  POPULAR  PHYSIOLOGY. 

which  only  allows  the  gullet  and  great  vessels  to  pass  through  it. 
At  the  top  also  it  is  shut  in  by  flesh  and  membrane,  which  allow  the 
gullet  and  windpipe  to  enter  and  the  large  arteries  and  veins  to  make 
their  escape.  Ihereibre,  since  the  windpipe  is  the  only  channel  that 
communicates  on  the  one  hand  with  the  lungs,  and  on  the  other 
with  the  atmosphere,  it  follows  that  through  it  alone  air  can  enter 
the  chest. 


Fig.  41.— Chest  of  Man.-a,  a,  Backbone  ;  b.  Breastbone ;  c,  c,  Ribs ;  d,  Collar- 
bone; e,  e,  Muscles  connecting  Ribs  ;  i,  Muscles  which  raise  the  first  and  second 
Ribs  ;  c1,  cf,  c1,  the  Diaphragm  or  fleshy  partition  j  h,  Sinews  of  the  same.— The 
dotted  line  represents  the  position  of  the  Diaphragm  on  the  right  side. 

But,  since  the  lungs  are  themselves  air-tight,  it  also  follows,  that 
nothing  can  pass  from  them  into  the  chest  (i.e.,  between  them  and  the 
ribs),  and  so  we  arrive  at  the  conclusion  that  the  chest  is  a  perfectly 
closed  cavity. 

Don't,  I  beg  of  you,  imagine  that  this  description  is  unnecessary. 
It  would  be  quite  impossible  without  it  to  make  you  realize  the  pro- 
cesses of  inspiration  and  expiration.  Even  still,  ere  you  can 
thoroughly  bring  the  thing  home  to  vour  minds,  it  is  requisite  that 
1  carry  you  two  steps  further.  First,  I  must  tell  you  that,  if  there  be 
placed  in  an  air-tight  chamber  a  bladder  which  opens  outwards,  and 


WHAT  IS  MEANT  BY  VACUUM. 


7.5 


that  you  try  fo  enlarge  this  cavity,  the  bladder  will  be  inflated. 
This  is  proved  experimentally  in  the  following  manner : — 

Take  a  hollow  cylinder  of  glass  (a),  fitted  above  with  a  cap  which 
is  pierced  by  a  tube,  to  which  a  bladder  (b)  is  firmly  tied  ;  let  there 
be  at  the  bottom  a  piston  (c)  with  a  short  handle,  and  have  the  whole 
apparatus  air-tight ;  then,  the  bladder  will  remain  as  represented  in 
fig.  42.  If,  however,  you  now  draw  down  the  piston  in  this  way, 
apparently  increasing  the  capacity  of  the  cavity,  the  bladder  will  be  at 
once  inflated.  To  one  who  is  entirely  unacquainted  with  pneumatics, 
this  seems  very  extraordinary.  It  is  not  so.  The  filling  of  the  bladder 
depends  upon  the  fact,  that  the  atmosphere 
presses  equally  in  all  directions.  Thus,  when 
the  apparatus  was  first  put  up,  the  air  in  the 
cylinder  pressed  against  the  outside,  and  that 
without  against  the  inside  of  the  membrane, 
with  equal  power ;  but,  when  the  piston  was 
depressed,  the  air  in  the  <  cylinder  became 
thinner ;  its  power  being  diminished,  the  re- 
sistance of  the  outer  air  overcame  it,  and  so 
the  bladder  was  blown  out  till  the  two  pres- 
sures again  balanced.  This  is  exactly  what 
takes  place  in  the  chest.  The  cavity,  during 
inspiration  or  drawing  in  the  breath,  is  en- 
larged, and  the  pressure  .of  the  atmosphere 
dilates  the  lungs,  filling  them  with  air.  1  dare 
fancy  you'll  tell  me,  you  knew  all  this  before. 
You  were  quite  aware  that  the  air  was  carried 
into  the  lungs  by  "  suction."  But  you  might 
as  well  have  said,  simply,  that  it  was  carried  in, 
for  the  word  suction  affords  no  explanation  whatever.  Torricelli,  a 
great  natural  philosopher,  gave  no  better  idea  of  the  real  cause,  when 
he  said  that  "  Nature  abhors  a  vacuum." 

We  have  got  the  right  leg  forward  now  that  we  know  so  much  ; 
the  left  will  follow  whilst  we  are  examining  the  contrivances  by  which 
the  enlargement  of  the  chest  is  effected.  Keep  one  eye  on  the  diagram, 
(fig.  41)  while  you  are  following  me  with  the  other.  Observe  the  way 
in  which  the  ribs  (b}  slope  downwards  from  back  to  breast-bone,  and 
mark  also  the  convex  dome  formed  _ by  the  great  fleshy  floor  or  dia- 
phragm (c  c'  c'},  and  you  will  agree  with  me  in  thinking  that  when  the 
latter  is  drawn  downwards  and  the  former  arc  elevated  the  cavity  of  the 
chest  will  be  much  increased  in  dimensions.  The  depression  of  the 
diaphragm  at  once  accounts  for  an  enlargement  of  the  chest,  for  the 
process  is  fairly  comparable  with  the  descent  of  the  piston  in  the 
cylinder ;  but  the  expansion  arising  from  the  elevation  of  the  ribs  is 
not  so  evident. 

First  let  me  show  you  how  the  ribs  are  elevated.  Each  rib  has 
a  sort  of  moveable  joint  situate  at  the  junction  with  the  backbone, 
and  this  permits  it  to  work  up  and  down  when  acted  on  by  the 
muscles.  Every  rib  is  connected  with  that  above  and  below  it  by 
layers  of  muscular  tissue,  and  the  upper  one  of  all,  or  first  rib,  as  it  is 


"- 

? 

r> 

^ 

1 

\c 

Fig.  42. 


76  POPULAR  PHYSIOLOGY. 

called,  has  attached  to  it  certain  band-like  muscles  which  arise  from 
the  vertebrae  of  the  neck,  (i)  When  the  band-like  muscles  contract, 
they  draw  up  the  lirst  ribs ;  and  the  muscular  tissue,  passing  from  these 
to  the  second,  the  second  to  the  next,  and  so  on,  being  contracted 
at  the  same  time,  the  whole  of  the  ribs  are  brought  more  into  the 
horizontal  position,  each  one  describing  a  part  of  a  circle,  of  which 
the  centre  is  the  joint  at  the  back.  The  leather  portion  of  a  large 
smith's  bellows  when  seen  at  work  gives  a  very  good  idea  of  the  rising 
of  the  ribs  ;  the  great  board  being  first  elevated  by  the  action  of  a 
lever,  and  then  the  various  folds  of  leather  ascending  slowly  one 
after  the  other.  By  this  elevation  of  the  ribs,  the  chest  increases 
more  in  width  than  in  length,  because,  as  the  ribs  pass  from  the 
inclined  to  the  horizontal  plane,  their  front  ends  become  more  distant 
from  the  backbone.  This  is  seen  in  the  accompanying  diagram,  where 
the  oblique  lines  represent  the  ribs  when  depressed,  and  the  hori- 
zontal ones  when  elevated  (fig.  43).  Should  you  require  a  more  tangible 
proof  of  this,  1  would  say,  take  a  pair  of  parallel 
rulers,  place  them  in  the  erect  position,  and  then 
the  oblique  connecting  rods  will  stand  for  the  ribs 
where  depressed.  Now  separate  the  two  bars,  let 
one  be  back  and  the  other  breast-bone,  and  as  soon 
as  the  rods  are  placed  horizontally,  you  will  find  a 
considerable  space  of  quadilateral  outline,  lying  be- 
tween them. 

The  diaphragm  is  more  constantly  employed  in  the 
labour  of  respiration  than  the  ribs,  and  during  its 
descent,  presses  upon  the  stomach  and  guts,  driving 
them  forward,  as  everybody  knows  by  experience. 
The  ribs  are  elevated  only  once  in  every  five  inspi- 
rations, and  then  "the  long  breath"  is  taken. 
Hitherto  I  have  been  speaking  of  inspiration,  but 
I  have  not  yet  touched  on  expiration,  because  it  is 
more  a  passive  action,  if  I  may  use  so  contradictory 
an  expression.  The  lungs  are  exceedingly  elastic,  and  this  elasticity 
must  be  overcome  in  their  inflation ;  from  which  it  results,  that  so 
soon  as  the  vanquishing  power  ceases  to  exert  itself,  the  tendency  to 
return  to  the  natural  condition  will  expel  all  air  which  has  been 
introduced  by  forcible  means. 

In  inspiration  the  diaphragm  contracts  and  descends,  and  the  rib- 
muscles  also  contract  and  elevate  the  framework ;  then,  the  pressure 
of  the  atmosphere  exceeds  that  of  the  lungs'  elasticity,  and  the  air 
rushes  in,  but  after  this  the  diaphragm  relaxes  and  ascends,  and  the 
ribs  descend,  and  now  the  lungs  of  their  own  intrinsic  strength  eject 
the  air  which  had  taken  "  forcible  possession  " — an  act  of  expiration 
has  been  performed. 

A  man  unfamiliar  with  the  object  of  the  balance-wheel  in  a  watch,  is 
given  a  "  movement "  in  which  this  mechanism  is  injured ;  the  injury 
being  evident,  he  winds  up  the  main-spring,  and  ere  he  has  removed 
the  key  is  aware  of  a  buzzing  noise,  and  beholds  the  hands  travelling 
with  fearful  rapidity  round  and  round  the  dial.  Instantly  the  idea  strikes 


Fig.  43. 


MECHANICAL  POWER  OF  LUNGS.  77 

him  that  the  balance-wheel  is  adapted  to  "regulate  the  time."  So  it 
is  in  our  complex  machinery ;  we  ourselves  are  ignorant  of  the  exact 
purpose  of  many  beautiful  appliances  till  they  are  disordered,  and 
then  we  perceive  by  the  effect  produced  on  the  general  system,  the 
advantage  of  what  might  have  previously  appeared  as  a  means  with- 
out an  end. 

To  illustrate  the  use  of  the  peculiar  pneumatic  contrivances  seen 
in  the  chest,  we  need  only  look  at  a  man  whose  lung  has  been 
wounded  (let  us  say  by  a  musket-ball).  The  cavitv  is  no  longer 
air-tight,  and  respiration  is  performed  with  great  difficulty,  the  air 
being  admitted  and  expelled  through  the  wounded  orifice  as  freely  as 
through  the  windpipe,  or  more  easily,  and  suffocation  not  unfrequently 
occurring  from  the  inability  to  form  a  vacuum,  and  by  that  means 
convey  the  gases  of  the  atmosphere  to  the  ultimate  cells. 

Some  conception  may  be  formed  of  the  immense  elastic  power  of 
the  lungs  themselves,  when  it  is  known  that  in  the  greatest  inspiration 
a  resistance  equivalent  to  150  Ibs.,  or  nearly  eleven  stone,  has  to  be 
overcome  in  the  male,  and  about  120  Ibs.  in  the  female.  This  is 
not  all,  there  is  also  a  great  amount  of  elastic  power  in  the  walls  of 
the  chest, — so  great,  that  to  overcome  it  a  force  of  104  Ibs.  is 
required  for  every  deep  inspiration.  Add  this  to  the  inherent  resist- 
ing power  of  the  lungs,  and  you  will  have  a  sum  of  254  Ibs.,  or  more 
than  18  stone,  .a  force  which  the  muscular  apparatus  of  the  chest 
exerts  whenever  you  draw  in  a  very  long  breath. 

It  seems  astounding  that  a  man  can,  with  his  ribs  and  diaphragm, 
exercise  an  amount  of  power  equal  to  that  of  a  coalheaver  when  he 
lifts  a  sack  weighing  21  c\vt.  upon  his  shoulders ;  yet,  that  this  state- 
ment is  not  fallacious  has  been  demonstrated  by  experiment.  The 
lungs  never  expel  all  the  air  which  they  contain  after  any  inspiration, 
for  it  is  found  that  the  lungs  of  man  can  hold  240  cubic  inches, 
and  those  of  _  woman  about  one  half  this,  whilst  there  is  ^little  more 
than  20  cubic  inches  drawn  in  and  sent  out,  ordinarily.  How 
then,  you  will  naturally  inquire,  is  the  impure  air  which  remains 
got  rid  of?  To  explain  this  1  must  digress. 

Chemists_  have  discovered  that  gases  invariably  mingle  with 
each  other  in  obedience  to  a  certain  Taw  termed  "  mutual  diffusion" 
For  instance,  carbonic  acid,  or  foul  air,  is  much  heavier  than 
the  atmosphere,  so  much  so  that  you  can  decant  it  from  one  vessel  to 
another,  as  you  would  water,  although  apparently  the  vessels  are 
empty.  Take  a  bottle  of  carbonic  acid  gas,  and  invert  it  over  a 
lighted  candle,  and  the  flame  will  be  instantly  extinguished.  And  since 
this  noxious  gas  is  perpetually  being  formed,  in  large  towns  more 
especially,  we  should  expect  that  eventually  it  would,  as  it  were, 
inundate  the  low  countries,  and  put  an  end  to  life.  Indeed  it  would 
do  so,  had  not  Providence  ordained  otherwise  by  this  statute  of 
"mutual  diffusion,"  "by  which  it  is  enacted"  that  all  gaseous  fluids 
of  different  weights— bulk  for  bulk— shall  so  mix  and  associate  with 
each  other,  that  destruction  of  life  may  be  avoided. 

The  following  very  interesting  experiment  shows  the  mode  of 
execution  of  this  law :  Let  a  glass  jar,  with  a  stop-cock,  be  filled 


PHYSIOLOGY. 


Fig.  44.— Spirometer,  or  instrument  for  measuring  the  capacity  of  the  Lungs 
for  air.  It  is  a  kind  of  gasometer.  When  air  is  blown  into  the  body  of  the  vessel, 
through  the  tube,  11,  17,  14,  19,  the  moveable  cylinder  is  elevated,  as  shown  at  B  ; 
and  as  it  rises,  it  marks  off  on  the  graduated  scale  the  number  of  cubic  inches  of 
air  it  has  received.  8,  9, 10,  11,  framework  supporting  the  weights,  12,  12,  which 
balance  the  moveable  cylinder;  18,  18,  pulleys  for  the  cords  ;  16,  aperture  through 
which  air  is  expelled  after  the  instrument  has  been  used ;  17,  the  stopper ;  15,  the 
scale  which  exhibits  the  amount  of  air  breathed  into  the  spirometer ;  13,  thermo- 
meter to  show  external  temperature ;  20,  the  moveable  cylinder  elevated  in  fig.  B  •, 
13,  tube  containing  coloured  alcohol,  to  indicate  the  relative  pressures  of  the 
air  within,  and  external}  4  and  5,  cocks  for  the  removal  of  water. 


PULMONARY  INHALATIONS  AND   EXHALATIONS. 


79 


with  carbonic  acid,  and  placed  in  the  usual  position;  then  let  a 
second  vessel  of  the  same  sort  be  filled  with  the  lightest  of  all  gases 
— hydrogen,  and  let  this  be  inverted,  the  two  stop-cocks  being 
united.  Next,  let  the  cocks  be  opened,  and  the  apparatus  left  to 
stand  for  some  hours ;  after  which  time  it  will  be  found  by  chemical 
tests  that  the  heavy  gas  has,  to  a  certain  extent,  ascended,  and  is 
present  in  the  upper  jar,  and  the  lighter  one  has  come  down,  and 
may  be  detected  in  the  lower  one. 

Revenons  a  nos  nmitons — or  to  apply  the  information  we  have 
just  arrived  at  to  the  function  of  respiration,  I  may  observe 
that  the  same  "law  of  diffusion"  is  applicable  to  the  gases  in 
the  lungs,  and  that,  although  but  twenty-two  cubic  inches  of 
air  enter  these  organs  at  each  inspiration,  yet  there  is  not  left  noxious 
gas  in  one  part  whilst  the  pure  fluid  circulates  through  another,  but, 
owing  to  this  principle  of  mingling,  a  semi-pure  atmosphere  is  supplied 
to  all  the  minute  compartments. 

For  what  purpose  is  all  this  complex  mechanism?  To  bring 
in  fresh  air,  and  send  out  the  impure.  What  is  the  use  of  the 
lung,  and  of  the  pure  air?  And  where  does  the  foul  air  come 
from?  Answering  these  queries  consecutively:  the  use  of  the 
lung  is  to  expose  the  blood  to  the  oxygen  of  the  air;  the  object 
of  the  air  is  to  purify  the  blood,  and  give  it  oxygen  for  the  tissues ; 
and  the  foul  air  arises  from  the  uncleansed  blood.  You  are  already 
conversant  with  the  course  of  the  venous  blood ;  you  know  that  it  is 
pumped  by  the  right  ventricle  to  the  lungs,  and  that  here  it  enters 
millions  of  microscopic  vessels,  which  lie  between  the  cavities  or  cells. 
In  these  localities  the  corpuscles,  highly  charged  with  carbonic  acid 
and  watery  vapour,  which  they  have  derived  from  the  tissue-refuse, 
meet  the  atmospheric  air — an  almost  inconceivably  thin  membrane 
intervening— and  a  species  of  osmose  takes  place,  the  carbonic  acid 
and  water  deserting  the  blood  disks,  and  the  oxygen  being  simul- 
taneously absorbed. 

This  change  occurs  at  every  inspiration,  and  is  accompanied 
by  an  alteration  of  colour— the  corpuscles,  from  having  been  before 
of  a  bluish  purple,  now  assume  the 
florid  hue,  and  pass  away  to  the  left 
side  of  the  heart  to  make  way  for  the 
venous  impure  fluid  behind  them.  So 
you  see,  when  the  breath  is  drawn  in 
the  interchange  begins,  the  pure  air 
is  absorbed  and  carried  away  by  the 
blood  into  the  system, -and  the  impure 
fluid,  the  vapour,  and  some  organic 
matter  are  expelled  in  the  expiration. 
To  prove  that  these  materials  are 
emitted  by  the  breath,  perform  the 
following  experiment.  Take  two 
bottles,  connected  as  shewn  in  the  diagram  (fig.  45),  by  corks  and 
tubes :  place  in  one  (a)  some  clear  oil  of  vitriol,  and  in  the  other  (b) 
a  small  quantity  of  lime-water,  and  then  expel  the  air  from  your 


Fig.  45. 


POPULAR  PHYSIOLOGY. 

lungs  through  them,  for  about  a  dozen  expirations,  and  you  will 
obserye  that,  first,  moisture  has  collected  on  the  sides  of  a;  second, 
the  oil  of  vitriol  has  become  blackened  ;  and  third,  the  lime-water, 
which  was  before  quite  transparent,  presents  a  milky  appearance, 
which  three  phenomena  demonstrate,  that  the  breath  contains  water, 
organic  matter,  and  carbonic  acid  ;  for  organic  matter  blackens  oil  of 
vitriol,  and  carbonic  acid  whitens  lime-water.  It  was  formerly  sup- 
posed that  the  carbonic  acid  which  emanated  from  the  lungs  was 
formed  in  these  organs,  that  the  venous  blood  contained  a  large 
quantity  of  charcoal  matter,  or  carbon,  which  combined  directly  with 
the  oxygen  of  the  air  —  in  fact,  that  combustion  took  place  in  the 
lungs  themselves.  This  view,  when  I  come  to  speak  of  the  cause  of 
animal  heat,  we  shall  perceive  to  be  incorrect,  but,  in  the  meantime, 
on  the  supposition  that  it  is  not  erroneous,  let  us  try  an  experiment 
to  test  its  truth.  If  the  combination  originates  in  the  lungs,  it  does 
so  because  the  carbon  of  the  blood  unites  with  the  oxygen  of  the  air; 
thus 


If,  then,  we  cause  an  animal  to  respire  a  gas  which  does  not  contain 
a  trace  of  oxygen,  it  is  evident  that  carbonic  acid  cannot  be  generated. 

Experiment  :  Place  a  bird  in  a  glass  jar  filled  with  pure  hydrogen  gas, 
in  which  it  will  live  for  a  short  time,  and  after  it  has  remained  for  a 
certain  period  remove  it,  and  carbonic  acid  will  be  found  in  the  vessel. 
Therefore,  we  see  that  it  is  not  formed  in  the  lungs,  but  in  different 
parts  of  the  body,  and  on  its  arrival  at  the  pulmonary  organs  is 
simply  discharged  from  the  blood—  oxygen  taking  its  place. 

Up  to  this  we  have  been  regarding  the  air  as  composed  of  oxygen 
alone,  and  we  have  been  doing  so  for  the  sake  of  simplicity  ;  that  it 
is  really  a  mixture  of  two  gases  I  dare  say  most  of  my  readers  are? 
aware. 


The  atmosphere  contains  in  100  parts  j 

with  just  a  vestige  of  carbonic  acid,  and  a  variable  quantity  of  oxysren 
in  disguise,  and  with  concentrated  power,  known  as  ozone.  The 
properties  of  these  two  chief  constituents  are  exactly  opposite  ;  thus, 
oxygen  supports  life  and  flame  ;  nitrogen  extinguishes  both.  The 
first  is  the  great  vivifier,  and  if  breathed  in  its  purity  would  cause 
the  vital  processes  to  be  carried  on  with  too  great  a  velocity  ;  the 
second  possesses  negative  qualities,  and  its  use  is  to  dilute  the 
oxygen,  in  order  that  the  animal  and  vegetal  functions  may  be  per- 
formed steadily. 

The  relative  actions  of  the  two  gases  are  well  exhibited  by 
igniting  two  pieces  of  phosphorus,  and  dipping  one  into  a  jar  of 
oxygen  and  the  other  into  a  vessel  of  nitrogen  ;  the  first  will  burn 
with  such  brilliancy  that  the  eye  can  with  difficulty  gaze  upon 
it,  the  second  will  be  instantly  extinguished.  The  two  fluids  are 
only  mingled  in  the  atmosphere,  not  chemically  combined,  and  an 


INFLUENCE  OF  CARBONIC  ACID  ON  LIFE.  81 

artificial  mixture  of  the  two  will  form  a  gas  indistinguishable  from 
ordinary  air.  It  is  sufficient  to  excite  our  astonishment  to  know  that 
in  the  cpurse  of  a  single  year  we  consume  100,000  cubic  feet  of  air, 
and  purify  about  3,500  tons  of  blood.  An  animal  may  be  suffocated 
from  absolute  want  of  oxygen  in  the  atmosphere ;  but  even  when 
this  gas  is  abundant,  the  presence  of  a  certain  proportion  of  carbonic 
acid  may  produce  smothering  also,  as  we  know  from  the  reports  of 
the  many  cases  of  charcoal  poisoning  which  have  occurred  in  France. 
If  a  sparrow  be  placed  under  a  bell-glass,  it  is  found  that  after  a 
certain  period  he  dies  of  suffocation ;  if,  however,  there  be  placed 
also  beneath  the  jar  some  substance,  such  as  potash,  which  will  absorb 
the  carbonic  acid,  life  is  preserved  for  a  much  greater  length  of  time. 
How  it  is  that  the  presence  of  foul  air  operates,  is  not  well  under- 
stood. Some  have  attempted  to  show  that  it  prevents  diffusion, 
but  the  arguments  in  support  of  this  idea  are  anything  but  satisfac- 
tory, and  it  is  far  more  likely  that  it  exerts  a  peculiar  poisonous  action 
on  the  lungs,  in  this  way  depressing  their  power  of  performing  the 
proper  function.  That  it  gradually  lowers  the  various  animal  pro- 
cesses, is  evident  from  the  effect  produced  on  persons  who  have  been 
respiring  a  vitiated  atmosphere.  For  example,  in  ah  overcrowded 
church,  or  theatre,  or  concert  hall,  who  has  not 

"most  somniferously  sleepy  felt  ?" 

A  curious  fact  in  connection  with  this  sensation  of  drowsiness  is  that 
you  gradually  become  habituated  to  the  locality,  your  instincts  of 
suspicion  regarding  the  danger  of  your  position  are  lulled  to  rest,  and 
death  is  steadily  creeping  over  your  frame,  whilst  you  are  quite  un- 
conscious of  his  approach.  Yet,  if  a  second  person  enters  the  room 
whose  atmosphere  you  have  been  tranquilly  and  unsuspectingly 
respiring,  he  is  instantly  warned  of  the  danger,  a  sense  of  suffocation 
oppresses  him,  and  he  rapidly  withdraws.  Your  lungs,  by  the  gradual 
and  uniform  depression  of  their  activity,  have  become  inured  to  the 
conditions  which  surround  you,  while  his,  in  the  midst  of  their 
activity,  have  received  a  sudden  and  severe  shock.  An  ingenious 
experiment  of  a  great  French  physiologist  demonstrates  this  more 
fully.  A  sparrow  is  placed,  as  in  the  last  instance,  beneath  a  bell 
glass,  and  retained  there  till  life  begins  to  wane ;  he  is  then  removed, 
and  rapidly  recovers ;  if,  however,  another,  a  vigorous  and  healthy 
bird,  be  introduced  into  the  atmosphere  vitiated  by  the  first,  he  almost 
instantly  expires. 

The  importance  of  attention  to  ventilation  cannot  be  over-rated, 
and  we  do  not  require  to  be  reminded  of  such  sad  occurrences 
as  those  in  the  "  Black  Hole  of  Calcutta,"  to  appreciate  the  advan- 
tages resulting  from  a  suitable  supply  of  fresh  pure  air.  It  is 
to  be  lamented  that  hygiene  is  so  much  neglected  as  a  science 
in  this  country ;  and  especially  that  hospitals,  asylums,  and  work- 
houses should  be  erected  on  sites  chosen  (as  often  happens)  by 
individuals  who,  either  through  ignorance  or  prejudice,  are  unfitted 
to  make  a  proper  selection.  It  is  melancholy  to  reflect  upon  the 
fearful  consequences  of  inattention  to  the  sanitary  condition  of  the. 

G 


82  POPULA.ll  PHYSIOLOGY. 

"lane  and  alley"  portions  of  our  large  towns.  Typhus,  cholera, 
scarlatina,  and  such  like,  are  in  many  instances  the  offspring  of  filth ; 
and  that  filth  in  its  most  loathsome  and  obscene  forms  exists  in  the 
purlieus  of  large  towns,  I  think  few  will  deny.  The  larger  streets, 
through  which  my  lord's  carriage  rolls,  are  paved  and  drained,  and 
swept  and  watered ;  but  the  narrow  entries,  the  obscure  side  streets 
where  the  poor  reside,  and  from  which  the  stench  proceeding 
is  often  intolerable  to  all  but  those  inured  to  it— who  cares  for 
these?  The  corporation?  No;  your  big-bellied  alderman,  and 
bloated  mayor,  cannot  be  seen  in  such  disreputable  localities !' 
Their  duties  relate  to  the  public— but  then  those  common  people!  you 
know  it  is  utterly  impossible  to  teach  them  cleanliness!  Oh,  of 
course,  of  course,  Mr.  Mayor ;  but  might  I  ask  you  when  did  you 
make  the  attempt  ?  If  it  be  deemed  advisable  that  borough  analysts 
should  be  appointed  to  prevent  the  imposition  of  adulterated  sub*- 
stances  upon  the  public,  which,  when  practised  even  extensively, 
injures  even  at  the  worst  but  a  few,  how  much  more  it  is  to  be 
desired  that  some  fit  person  be  employed  to  see  that  as  little  adulte- 
ration as  possible  of  the  air  we  breathe—  of  the  food  of  all,  from  the 
king  to  the  beggar — be  admitted !  Dear  reader,  if  you  have  ever 
experienced  the  atmosphere  which  prevails  in  the  dens  of  the  poor — 
if  you  have  ever  toiled,  flight  after  flight,  over  the  ricketty,  rotten 
staircases  of  obscure  lodging-houses,  and  entered  the  gloomy,  ill- 
lighted,  ill-ventilated  apartment  of  some  dying  patient,  and  observed 
parents  and  children  huddled  together  in  sickness,  squalidness,  and 
misery — you  will  forgive  me  this  digression. 

The  way  in  which  we  breathe  has,  I  trust,  been  already  made 
sufficiently  apparent ;  the  reason  why  we  do  so  is  not  quite  so  evi- 
dent ;  in  fact,  if  truth  must  be  told,  is  not  known  at  all.  I  do  not 
mean  to  say  that  it  has  not  been  explained ;  for  I  believe  there  is  hardly 
a  work  on  physiology  extant  but  what  contains  a  lengthy  explana- 
tion (?)  of  the  cause. 

Don't  for  a  moment  suppose  that  I  would  accuse  the  philosophic 
authors  of  endeavouring  to  deceive  the  public ;  but  this  is  pretty 
certain,  if  they  did  not  intend  to  confuse  their  readers,  they 
assuredly  have  obfuscated  themselves.  A  recent  book-maker  seems 
to  have  discovered  the  entire  case,  for  he  writes  in  the  most  un- 
hesitating manner, — "The  respiratory  acts  are  automatic,  occurring 
without  our  being  aware  of  them;"  of  course,  the  question  is 
a  delicate  one,  but  since  the  gentleman  is  not  aware  of  the 
existence  of  his  own  respiratory  movements,  I  should  like  to  inquire 
how  he  obtained  the  information.  Further  on  he  observes  of  the 
respirationSj  that  they  are  "  produced  by  the  unserated  blood  in  the 
lungs,"  giving  rising  to  a  "  oesoin  de  respirer."  This  is  cloaking 
one's  ignorance,  with  a  vengeance.  The  unserated  blood  producing 
a  necessity  for  breathing  is  the  reason  why  we  do  breathe.  1  need  n9t 
remind  the  reader  of  a  certain  animal  which  once  disguised  itself  in 
the  skin  of  a  lion,  and  through  its  peculiar  vocal  intonation  confessed 
its  real  character ;  but  it  does  strike  me  that  the  above  philosophic 
generalization  is  a  suggestive  one. 


THE  ORGANS  OP  VOICE.  83 

External  impressions  often  bring  about  the  action  of  the  lungs 
when  it  has  apparently  ceased ;  thus,  water  thrown  upon  the  face 
or  chest  of  one  who  has  just  fainted,  rouses  the  dormant  power 
and  restores  consciousness  of  surrounding  objects.  Similarly  in  the 
newly-born  infant  the  function  of  respiration  is  stimulated  to  per- 
f9rmance  by  the  influence  of  the  cold  air  upon  the  face,  or  artifi- 
cially, by  a  not  over  gentle  thwack  imparted  to  the  more  ignoble 
extreme  by  the  hand  of  the  attendant  "  bairey  Gamp,"  if  so  to  do 
"  dispoged."  Of  the  way  in  which  this  external  stimulus  acts,  or  the 
road  by  which  the  effect  is,  so  to  speak,  conveyed  to  the  lungs,  we 
know  literally  nothing. 

As  bearing  on  the  subject  of  respiration,  I  think  we  may,  with 
advantage,  here  consider  the  kindred  one  of  voice.  I  must,  however, 
premise  my  remarks  by  telling  you  that  the  country  we  are  about  to 
explore  is  not  a  very  level  one,  but  with  hill  and  dale,  upland  and 
low,  mountain  and  moor;  so  that  though  we  travel  through  the 
different  districts,  the  contour  of  the  surface  is  so  varied— I  might 
almost  say  so  complex— that  at  the  end  of  the  journey  you  will  not 
acquire  so  much  information  as  possibly  you  anticipate. 

"Voice  is  a  general  term,  and  includes  under  it  two  forms :— first,  voice 
proper,  or  mere  musical  sounds ;  second,  the  different  classes  of  articu- 
lation or  speech.  And  we  find  that  voice  and  speech,  although  both 
due  to  the  expulsion  of  air  from  the  windpipe,  yet  are  produced  by 
two  distinct  sets  of  apparatus ;  the  former  owing  its  production  to 
the  larynx,  the  latter  to  the  mouth  and  tongue.  Two  experiments 
demonstrate  the  truth  of  this  statement.  If  an  opening  be  made 
into  the  windpipe,  below  the  larynx,  voice  is  lost  so  long  as  the 
incision  allows  the  air  to  pass  through  it.  And  to  prove  that  the 
utterance  of  words  is  owing  to  the  mouth  and  tongue,  a  tube  has 
been  introduced  through  the  nostril*  so  as  to  reach  the  back  of  the 
mouth,  then  the  breath  having  been  held,  air  has  been  blown  through 
this  tube,  and,  by  the  evolutions  of  tongue  and  lips,  sentences  have 
been  uttered  in  a  faint  whisper. 

The  larynx  is  an  apparatus  composed  of  an  intricate  assemblage  of 
muscles,  gristly  rings,  and  membrane.  It  stands  on  the  upper  end  of 
the  windpipe— to  which  it  is  joined— as  a  statue  rests  on  its  pedestal ; 
and  above  it  is  covered  by  the  root  of  the  tongue.  Its  largest  cartilage 
(or  gristle),  the  thyroid^  (b  b  fig.  46),  is  one  with  which  everybody  is 
familiar  under  the  name  ot  Adam's  apple,  but  which  is  not  confined  to 
man,  being  developed,  though  to  a  lesser  extent,  in  woman  also.  This, 
at  the  top,  forms  the  doorway  of  the  organs  of  respiration.  But  this 
doorway  is  a  "trap,"  that  is,  it  does  not  stand  vertically,  so  that  the 
tenant  can  enter  and  depart  in  the  erect  posture,  but  is  horizontal, 
so  that  he  must  go  out  head  foremost.  Its  sides,  or  "  jambs,"  are  com- 

*  That  a  communication  between  the  back  of  the  mouth,  or  pharynx, 
and  the  nostril  does  exist,  the  reader,  who,  in  an  explosion  of  laughter  at 
the  breakfast  table,  has  sent  his  coffee,  via  his  nose,  into  his  pocket- 
handkerchief,  will  at  once  admit. 

f  From  two  Greek  words,  signifying  a  "  shield  "  and  "  like." 
G2 


84 


POPULAR  PHYSIOLOGY. 


posed  of  two  folds  of  membrane,  meeting  to  a  point  in  front,  and  sepa- 
rated behind,  which  are  termed,  improperly,  vocal  chords  (e  e,  fig.  47). 
These,  by  means  of  peculiar  contrivances,  can  be  shortened  and  approxi- 
mated, so  as  to  alter,  within  certain  limits,  the  size  of  the  aperture, 
which  is,  as  you  will  have  concluded,  of  a  triangular  outline.  So  much 
for  the  doorway.  It  opens  into  the  throat,  or  highway  leading  to  the 
gullet,  and,  on  that  account,  an  eccentric  or  vagabond  morsel  of  food 


Fig.  46. 


Fig:.  47. 


Fig.  46. — Human  Larynx,  seen  from  the  front.  Fig.  47. — Same  seen  from 
above,  a,  the  ring-gristle  ;  b,  b,  the  thyroid ;  c,  c,  the  pyramidal  levers ;  d,  the 
epiglottis  j  e,  e,  and/,/,  the  vocal  chords. 

often,  regardless  of  its  proper  destination,  might  succeed  in  gaining 
admission  to  the  lungs  and  doing  a  deal  of  mischief,  were  it  not  for  the 
door  which  is  closed  against  it.  This  door  is  called  by  anatomists  the 
epiglottis*  (d,  fig.  47) .  It  is.  in  outline,  like  a  heart-shaped  leaf,  is  hinged 
at  its  point  to  the  front  of  the  ring  known  as  Adam's  apple,  and  laps 
when  closed,  over  the  doorway  and  its  sides,  the  vocal  chords,  as 
shown  above.  This  closure  or  the  epiglottis  takes  place  on  every 
occasion  of  swallowing,  and  so  food  particles  of  a  migratory  turn  are 
prevented  passage  into  the  windpipe  and  wend  their  way  stomach- 
ward.  The  mechanism  by  which  the  "vocal  chords  are  brought 
together  and  separated  is  ingenious  and  interesting.  In  front,  as  I 
mentioned,  the  two  cords  (e  e,  fig.  47)  are  attached  to  the  "  ppmuni 
Adami ; "  behind,  however,  where  they  divaricate,  each  is  conjoined 


*  Epi,  upon,  and  glottis,  tongue ;  a  derivation  which  affords  a  miscon- 
ception as  to  the  true  position  of  the  structure  alluded  to. 


MECHANISM  OF  THE  VOCAL  CHORDS. 


85 


with  a  little  gristly  pyramid  (cc,  fig.  47),  being  united  to  one  of  the 
corners  at  the  base,  and  since  each  pyramid  moves  on  a  central  pivot, 
and  various  muscles  are  connected  with  the  sides  and  other  portions, 
it  will  be  readily  seen  that  by  the  movements  of  the  pyramids  in  one 
direction  or  the  other  the  chords  will  be  separated  or  approximated. 

The  pyramid  is  a  lever  of  the  first-class,  like  that  of  an  ordinary 
balance  ;  when  one  end  is  pulled  inwards,  the  other  is  moved  out,  and 
vice  versa ;  and  as  the  vocal  chords  are  attached  to  one  extremity  of 
each,  they  necessarily  are  caused 
to  approach  or  diverge  according 
to  the  direction  in  which  the  py- 
ramids are  drawn. 

When  it  is  required  to  tighten 
the  cords,  the  gristle  (b  b,  fig.  46) 
to  which  they  are  attached  in 
front  is  drawn  downwards  by  a 
special  muscle.  Thus  we  per- 
ceive that  this  orifice,  guarded 
at  its  sides  by  the  vocal  chords, 
is  capable,  by  an  approach  of 
these  latter,  of  being  diminished 
in  size,  and  of  being  also  made 
tense  or  slack  as  is  needed. 

Have  you  ever  opened  an  accor- 
dion or  concertina,  and  seen  all 
the  brass  tongues  of  different 
sizes,  by  the  vibration  of  which 
the  various  notes  are  produced  ? 
If  so,  you  can  at  once  catch  the 
meaning  of  the  human  hautboy — 
the  vocal  chords — for  these  are 
not  to  be  likened  to  a  pair  of 
strings,  nor  to  the  flute  pipes  of 
an  organ  as  is  occasionally  done. 
They  constitute  really  a  sort  of 

reed,  which  by  virtue  of  the  ap-  Fig.  48  represents  the  head  of  a  corpse 
piiances  1  have  been  describing,  arranged  for  experimentation  on  the 
Can  be  made  large  or  small:  and  organs  of  voice,  a  b,  the  throat;  c,  the 
this  shortening  pan  tal-p  nlapp  tn  toP  of  windpipe;  d,  an  apparatus  by 

take  place  to  means  of  which  the  orifice  of  the  larynx 

an     almost    inconceivably    slight  can  be  altered  in  size ;  e,  a  string  which 

extent,  as  we  shall  see  presently,  passes  over  a  pulley  and  has  attached  to 

In  man  each    chord  measures  *  a  scale  pan  ;  by  placing  a  weight  in  the 

cPTrpnfv  +  WP   VinnHvorH^o   r>f    or,  latter,  the  string  is  made  tense,  and  the 

seventy-three  nundredths  ot  an  Adam's  apple  brought  forward ,-/,  a  tube 
inch  when  relaxed,  and  when  most  connected  with  a  pair  of  bellows, 
tense  ninety-three  hundredths,  or 

about  one-fifth  of  an  inch  more;  and,  as  every  variety  of  sound  is  pro- 
duced by  a  shortening  or  lengthening  of  the  chords  within  the  limits  of 
that  one-fifth,  how  immeasurably  minute  must  be  the  difference  in 
length  necessary  to  the  production  of  two  distinct  sounds  in  the  same 
octave  ?  The  longer  the  chords  the  lower,  as  regards  the  musical 


86  POPULAR  PHYSIOLOGY. 

scale,  will  be  the  sounds  produced  by  them ;  and,  therefore,  as  a 
man's  voice  is  more  of  the  bass  kind  than  a  woman's,  we  find  his 
vocal  chords  to  be  the  longer  of  the  two.  In  the  female  they 
measure,  when  most  drawn  out,  only  sixty-three  hundredths  of 
an  inch.  Here  a  fact  suggests  itself :  a  boy  of  twelve  has  a  voice 
resembling  a  woman's,  but  at  the  age  of  fifteen,  or  thereabouts,  it 
"  cracks/'  and  becomes  coarser.  Why  is  this  ?  Because  at  the  same 
period  in  which  the  voice  alters  its  character,  the  Adam's  apple 
becomes  enlarged,  and  is  seen  to  project  further,  and  it  is  to  the 
inner  surface  of  these  the  chords  are  attached ;  so  that,  as  they 
follow  the  advance  of  the  gristle,  they  increase  in  length,  and  hence 
the  voice  is  changed. 

The  compass  of  the  voice  of  an  amateur  singer  is,  at  the  lowest, 
about  two  octaves,  each  of  which  is  equivalent  to  about  twelve 
semitones,  and  since  it  is  possible  easily  to  produce  ten  dis- 
tinct musical  sounds  within  each  semitone,  the  number  of  distinct 
intonations  which  may  be  produced  by  the  organs  of  voice  can 
fairly  be  set  down  as  two  hundred  and  forty.  Now  these  are,  as 
you  know,  produced  by  different  degrees  of  shortening  or  length- 
ening on  the  part  of  the  chord,  and,  as  the  limit  of  increase  or 
decrease  is  one-fifth  of  an  inch,  it  is  clear  that  in  passing  from  one 
sound  to  that  immediately  above  or  below  it,  the  chords  are 
diminished  in  length  or  elongated  by  the  two-hundred-and-fortieth 
of  one-fifth  of  an  inch,  or,  in  other  words,  the  one-twelve-hundredth 
of  an  inch.  From  what  is  known  of  the  vocal  powers  of  the  dis- 
tinguished Madame  Mara,  it  has  been  calculated  that  her  voice- 
chords  can  only  have  been  altered  in  length,  by  about  the  ten- 
thousandth  of  an  inch  in  the  production  of  each  separate  sound. 
These  facts  are,  indeed,  sufficient  to  arrest  ^ur  thoughts,  and  should 
teach  us  to  reflect  upon  the  wondrous  foresight  and  intelligence  of  the 
Almighty  Jehovah.  We  are  told  with  astonishment  of  the  extraor- 
dinary adapting  power  of  Nasmyth's  steam-hammer,  which  can  crush 
an  anchor^or  drive  a  nail  with  ^  equal  facility;  but  what^is  it  in  com- 
parison with  this  little  mechanism — the  organ  of  voice — in  which  two 
simple  folds  of  membrane  can  be  tensed  or  relaxed  to  the  ten- 
thousandth  of  an  inch  with  the  most  mathematical  exactitude,  and 
which,  in  those  that  have  the  mighty  gift  of  song,  can  send  forth — 

"  Such,  floods  of  delirious  music, 
That  the  whole  air,  and  the  woods,  and  the  waves  seem  silent  to  listen." 

Some  persons  are  remarkable  for  the  loudness  of  their  voices, 
others  for  the  softness,  and  though  these  qualities  are  said  to  depend 
upon  the  force  with  which  the  air  is  driven  from  the  lungs,  it  seems 
more  probable  that  they  are  due,  as  it  were,  to  the  echoing  power  of 
the  larynx  itself;  for  in  monkeys  called  Mycetes,  which  inhabit 
America,  there  are  hollow  sacs  attached  to  the  gristles  of  the  vocal 
organs,  and  the  effect  of  which  is  to  render  the  howling  of  these 
creatures  a  source  of  great  terror  to  travellers,  it  being  asserted  that 
their  nocturnal  concerts  may  be  heard  for  miles,  the  sounds  being 
even  more  powerful  than  the  roaring  of  Herr  Eormes,  or  the  lion 


SPEECH — VENTRILOQUISM  —WHISTLING.  87 

itself.  The  cause  of  variation  in  the  "  timbre  "  of  the  voice  appears 
to  be  a  difference  in  the  amount  of  hardness  or  softness  of  the  organs, 
but  of  this  we  know  nothing  with  certainty. 

This  is  the  place  to  say  a  few  words  about  speech.  Sentences  are 
combinations  of  words,  these  latter  of  syllables,  and  syllables  of 
sounds.  Now  how  do  we  make  those  different  sounds  ?  The  vowels 
are  formed  simply  by  the  increase  or  decrease  in  sizt  of  the  mouth, 
or  by  an  alteration  of  its  shape.  The  consonants  are  formed  by  various 
movements  of  the  tongue  and  lips,  as  the  reader  may  see  for  himself 
by  "running  through"  the  alphabet,  and  marking  the  process  by 
which  each  sound  is  produced.  That  speech  results  from  move- 
ments of  the  tongue  and  lips  has  been  demonstrated  ingeniously 
by  the  invention  of  speaking  machines,  which  have  been  exhibited 
from  time  to  time,  one  of  which  was  so  perfect  that  it  could  utter 
many  distinct  sentences,  and  among  others,  "I  love  you  with  all  my 
feeart." 

Stammering  is  caused  by  a  want  of  control  over  the  muscles  em- 
ployed in  the  pronuncia^n  of  certain  letters,  and  is,  to  all  intents 
and  purposes,  similar  in  its  origin  to  the  disease  called  St.  Vitus's 
dance,  in  which  it  is  found  impossible  to  govern  the  movements  of 
the  muscles  of  the  limbs.  Of  this  we  may  be  assured,  that  the  only 
cure  for  the  stutterer  is  caution  in  spe  aking  and  reading.  Let  him,  if 
possible,  feel  assured  that  he  has  the  power,  but  let  him  exert  it 
slowly  and  with  care.  Ventriloquism  is  a  faculty,  the  nature  of  which 
every  one  is  conversant  with ;  but  when  we  come  to  inquire  how  the 
peculiarly  deceptive  voice  is  produced,  we  are  somewhat  in  a  diffi- 
culty. One  great  physiologist  prides  himself,  doubtless,  upon  the 
discovery  that  ventriloquism  is  only  the  imitation  of  sounds  produced 
at  a  distance ;  but  I  fancy  many  of  my  readers  have  made  the  same 
discovery,  which  is,  at  best,  but  an  expression  of  the  deceptive  powers 
exhibited  by  professors  of  the  art.  The  derivation*  of  the  word 
would  imply  that  speaking  in  the  stomach  was  the  power  of  those 
gifted  with  the  ventriloquistic  faculty  ;  but  a  mere  tyro  in  anatomy 
would  perceive  at  once  the  utter  absurdity  of  such  an  opinion.  The 
German  view  is  certainly  the  most  probable  one.  It  is  this  :  the  sounds 
of  the  ventriloquist  are  produced  by  taking  a  deep  inspiration,  in 
doing  so,  depressing  the  diaphragm  and  protruding  the  abdomen,  and 
then  breathing  out  slowly  by  compressing  the  lungs  with  the  lateral 
portions  of  the  chest— the  sounds  being  modified  by  the  mouth  as  in 
the  case  of  ordinary  speech. 

Whistling  is  the  production  of  musical  sounds  by  forcing  the  air 
rapidly  through  a  small  orifice  formed  by  the  two  lips.  It  is  due  to  the 
series  of  vibrations  into  which  the  current  of  air  is  thrown  in  passing 
from  the  mouth ;  because,  if  air  be  driven  with  rapidity  through  the 
mouthpiece  of  a  flute,  a  similar  series  of  sounds  is  developed  by 
altering  the  aperture. 

Sighing  is  caused  by  any  circumstance  which  tends  to  depress  the 
system,  and  is  a  form  of  deep  inspiration,  which  originates  in  a  waut 

*  From  venter,  stomach,  and  loquor,  I  speak. 


88  POPULAR  PHYSIOLOGY. 

of  air  in  the  blood.  Thus,  if  a  person  be  very  much  absorbed  by  any 
subject,  the  nervous  power  is,  so  to  speak,  drawn  from  the  pulmonary 
organs  into  some  other  channel,  and  afterwards,  to  C9mpensate  for 
the  feeble  exertion  of  the  lungs,  a  series  of  deep  inspirations  follows — 
the  individual  sighs.  So  that,  as  Mr.  Lewes  truly  observes,  "  the  phi- 
losopher brooding  over  his  problem  will  be  heard  sighing  from  time 
almost  as  deeply  as  the  maiden  brooding  over  her  forlorn  condition." 

In  yawning  a  deeper  inspiration  is  taken  than  in  sighing ;  but  the 
cause  is  pretty  much  the  same.  Why  it  is  so  catching  is  quite  an 
enigma ;  and  much  as  men  may  talk  about  sympathies,  and  such  like, 
it  does  not  appear  that  we  are  able  to  solve  the  problem. 

Sobbing  ana  hiccup  are  expiratory,  or  breathing-out  actions,  when 
the  door  of  the  larynx  is  partially  closed.  Coughing  is  what  is 
termed  a  reflex*  action.  It  is  produced  by  some  substance — 
mucus,  cold  air,  food,  &c.— irritating  the  larynx,  windpipe, or  bronchial 
tubes.  The  irritation  stimulates  the  muscles  of  the  chest  and  the 
diaphragm,  which  then  contract  violently  in  order  to  expel  the  in- 
truder. It  is  called  reflex  from  a  peculiar  view  as  to  the  way  in 
which  the  effect  of  the  irritant  is  transmitted.  Thus  in  the  spinal 
chord  lies  the  power  of  bringing  into  play  the  muscles  employed  in 
respiration,  and  it  calls  this  power  into  operation  by  means  of  nerves 
passing  from  it  to  the  parts  alluded  to.  But  it  also  has  the  power  of 
receiving  impressions  through  nerves  which  travel  to  it  from  the 
lungs,  larynx,  &c.  Now,  in  a  reflex  action,  the  irritant  (a  morsel  of 
food  which  has  lost  its  way)  produces  an  effect  upon  the  nerve  ;  this 
effect  is  conveyed  to  the  spinal  cord,  which  then  transmits  the  power 
to  the  muscles,  that  they  may  expel  the  stranger — the  impression 
being  as  it  were  reflected. 

Sneezing  is  a  more  intense  form  of  expiration  than  coughing,  and 
is  similarly  caused,  the  irritant  particle  being  in  this  case  situate  in 
some  portion  of  the  nostril.  That  it  may  arise  from  the  irritation  of 
other  parts  is  also  certain— a  distinguished  German  physiologist 
being  obliged  to  sneeze  whenever  the  bright  light  of  the  sun  falls 
upon  his  eyes.  The  use  of  the  pocket-handkerchief,  and  indul- 
gence in  a  hearty  blow  of  the  nose,  is  often  sufficient  to  terminate  a 
fit  of  sneezing;  and  I  can  particularly  commend  the  practice  to  those 
elderly  gentlemen  who  are  the  terrors  of  the  tea-table  when  they  com- 
mence, after  the  fashion  of  "  Mr  Staggers,"  looking  alternately  at 
their  friends  and  handkerchiefs. 

The  way  in  which  laughter  is  produced  has  not  been  clearly  made 
out ;  although,  doubtless,  this  very  statement,  from  its  apparent  un- 
truthfulness,  may  excite  a  smile.  Granted,  we  know  how  to  make  a 
friend  laugh ;  we  may  tickle  his  ribs  with  our  fingers,  or  his  fancy 
with  a  joke ;  but  we  cannot  tell  why  it  is  that  he  laughs,  after  all. 
The  most  plausible  explanation  is  this :  a  good  joke  gives  rise  at 
once  to  an  idea,  and  this  to  a  certain  quantity  of  nervous  force, 
more  or  less,  according  to  the  temperament  of  the  recipient.  This 
nervous  force,  having  been  developed,  must  be  expended,  and  the 

*  The  objections  to  this  view  would  not  be  adapted  to  appear  in  so 
popular  a  treatise  as  this. 


LAUGHTER— CONSUMPTION.  89 

expenditure  may  take  place  in  one  of  two  modes :— firstly,  in 
developing  a  series  of  new  ideas  till  it  is  exhausted — this  is  the  effect 
upon  a  thoughtful  man  of  a  nervous  temperament;  secondly,  by 
being  transmitted  to  the  muscles,  and  calling  them  into  play  as  in 
laughing.  But  you  will  say,  if  I  relate  a  funny  anecdote  to  a  man 
who  does  not  laugh  is  he  therefore  thoughtful  ?  No,  he  may  be  a 
man  of  lethargic  turn,  and  your  tale  has  developed  no  nervous  force 
at  all.  Why  does  not  the  nervous  force,  when  carried  to  the  muscles, 
affect  those  of  the  arm  and  leg  as  well  as  those  of  the  face  and  chest  ? 
This  is  a  very  fair  query,  and  I  admit  is  the  one  most  difficult  to 
answer.  Possibly  because  it  flows  into  the  nerves  of  the  face  and 
respiratory  organs  more  readily  than  it  could  pass  into  the  lower 
nerves,  and  so  affect  the  limbs  j  and  it  is  familiar  to  all  of  us  that 
when  there  is  an  exuberance  of  the  jocular  laughing  force,  it  does 
affect  the  limbs  also,  as  exhibited  in  that  tendency  to  throw  up  the 
arms  and  legs  when — 

"  O'er  all  the  ills  of  life  victorious." 

The  laughter  which  results  from  physical  tickling  would  come  under 
the  category  of  reflex  actions ;  and  as  we  cannot  explain  it,  we  shall 
leave  it,  along  with  many  other  vital  phenomena  enjoying  that  physio- 
logical limbo. 

Ere  we  conclude  this  chapter  on  respiration,  let  .me  caution  you 
against  confounding  two  very  distinct  diseases  of  the  lungs :  con- 
sumption or  phthisis,  and  bronchitis.  The  former  is  a  malady  affecting 
the  fine  tissue  of  the  organ— air  cells,  blood-vessels,  &c.  The  latter 
is  an  inflammatory  state  of  the  bronchial  tubes  and  windpipe.  Below, 
I  have  given  in  a  tabular  form  a  few  of  the  characters  of  each ;  but 
above  all  things  let  me  impress  upon  you  the  necessity  of  consulting 
a  physician  at  the  very  outset  of  either  disease,  for  of  "  all  the  ills  that 
flesh  is  heir  to  "  there  are  none  in  which  a  really  scientific  practi- 
tioner can  effect  more  for  the  patient  than  in  consumption  and  bron- 
chitis, if  the  case  be  undertaken  at  an  early  period  of  the  attack ;  and 
none  which  are  so  likely  to  be  confounded  by  the  unskilled.  An 
anxious  mother  may  think  her  daughter  consumptive  because  she  is 
subject  to  catarrh,  or  may  imagine  that  a  really  insidious  attack  of 
consumption  is  but  "A  mere  cold'3 

In  Consumption.  In  Bronchitis. 

1.  Shiverings  and  flushings.  1.  No  shiverings  or  flushings. 

2.  Cough  comes  on  in  middle  of    2.  Cough  on  rising  in  the  morning 

night,  or  toward  morning.  and  on  going  to  bed  at  night. 

3.  Pulse  is  very  rapid.  3.  Pulse  beats  as  usual. 

4.  Disease  of  the  stomach  and    4.  No  disease  of  stomach. 

loss  of  appetite;  and  in  fe- 
males general  derangement  of 
system. 

5.  Inability  to  eat  fats  and  sugar.    5.  No  distaste  for  fats  or  sugar. 

6.  Pain  in  upper  part  of  chest,    C.  Pain  of  itching  character,  just 

beneath  collar  bone.  beneath  breast  bone. 

7.  Very  often  diarrhoea.  7.  No  diarrhoea. 


90  POPTJLA.ll  PHYSIOLOGY. 


CHAPTER    IX. 

Heat — Centigrade  and  Fahrenheit's  Thermometer — Why  we  feel  Cold — 
Normal  Temperature  of  the  Body — Theory  of  Combustion  in  the 
Lungs — Doctrine  of  Liebig — Heat  without  Flame — Heat-forming 
Foods— Sources  of  Animal  Heat — Influence  of  the  Sympathetic  Nerve 
— Tolerance  of  intense  Heat  by  the  lower  Animals— The  "  Fire  King." 

MAN  is  a  warm-blooded  animal.  I  fancy  I  hear  the  reader  say  to 
his  less  learned  friend,  What  is  the  meaning  of  the  expression  warm- 
blooded ?  Having  the  blood  warm  ?  That,  my  dear  friend,  is  no 
answer  to  my  question  ;  for  you  are  still  unable  to  tell  me  what  being 
warm  is.  What  you  meant  when  you  said  warm-blooded,  was  this : 
the  circulating  fluid  is  of  a  greater  temperature  than  that  of  the  sur- 
rounding air.  ^  1  thrust  the  poker  in  the  fire  till  it  is  red  hot,  and 
then  lay  it  aside,  and  what  do  I  find?  The  fiery  metal  gradually 
becomes  black,  and  its  heat  passes  away  to  the  air,  and  to  everything 
in  its  neighbourhood,  till  at  last  it  is  quite  cold  again.  Is  this  the 
case  with  man  ?  You  will  reply,  Yes  ;  sometimes  he  is  hot,  at  other 
times  he  is  cold.  Wrong ;  his  blood  is  always  at  the  same  heat.  If 
a  thermometer  be  placed  under  your  tongue,  the  mercury  will  rise  in 
the  tube  till  it  stands  at  98  deg.,  but  it  will  go  no  higher  ;  nay,  if  you 
were  perched  on  one  of  the  glaciers  of  the  Alps,  or  were  being  broiled 
beneath  the  sun  of  Hindostan,  it  would  just  indicate  the  same  degree 
— 98.  Of  course  I  refer  to  Fahrenheit's  thermometer,  which  is  the 
one  usually  employed  in  this  country,  and  not  to  that  which  is  termed 
the  " centigrade''  In  our  thermometer  the  mercury  rises  to  the 
number  212  when  placed  in  boiling  water;  in  the  centigrade, 
however,  the  boiling  point  is  indicated  by  the  number  100 ;  so  that 
you  must  bear  in  mina  that  the  blood-heat  degree,  98,  of  the  thermo- 
meter employed  in  England  is  almost  the  boiling  one  of  the  French 
instrument. 

Some  years  since  a  gentleman  was  recommended  by  his  physician  to 
travel  to  the  south  of  France  for  the  benefit  of  his  health.  He  followed 
this  advice,  and  early  in  the  spring  set  out  upon  his  journey  to  the 
southern  provinces  of  that  country.  Shortly  after  his  arrival,  he 
determined  to  indulge  in  the  luxury  of  a  warm  bath,  and  on  being 
asked  by  the  bath  superintendent  at  what  temperature  he  required 
the  water,  replied  at  about  100  deg.  The  manager  mildly  expostulated 
with  him,  but  in  vain ;  and  I  suppose,  having  had  some  considerable 
experience  of  the  determination  characteristic  of  the  Anglo-Saxon,  at 
length  yielded  to  his  entreaty,  and  prepared  the  bath — muttering  to 
himself  as  he  went  out  that  the  poor  gentleman  would  certainly  be 
scalded.  The  Englishman,  however,  was  not  devoid  of  caution,  and 
being  led  to  suspect,  from  the  opposition  of  the  superintendent  and 
from  the  excessive  quantity  of  vapour,  that  something  must  be  amiss, 
quietly  dipped  in  his  great  toe  to  test  the  temperature,  and  finding 


HEAT— COLD— AGUE.  91 

to  his  dismay  that  he  had  been  on  the  verge  of  giving  himself  a 
lobster's  death,  left  the  establishment  much  discomposed,  and  on 
arriving  at  his  hotel  was  informed  of  his  mistake ;  which  mistake  was 
not  a  very  extraordinary  one,  but  such  as  the  reader  must  recollect 
when  desiring  to  enjoy  a  warm  bath  in  France. 

You  no  doubt  consider  it  very  strange  that  you  are  not  cold  when 
you  feel  cold,  nor  warm  when  you  experience  a  tendency  to  adopt 
Sidney  Smith's  recipe—"  take  oif  your  flesh,  and  sit  in  your  bones." 
Yet  such  is  the  trutli.  When  you  shiver,  you  are  really,  as  regards 
your  blood,  no  colder  than  when  you  felt  quite  comfortable  as  you  sat 
before  your  fire.  Sensations  of  heat  and  cold  are  of  course  common ; 
but  even  whilst  we  experience  them,  our  blood  is  not  colder  nor 
warmer  than  usual. 

We  say  we  are  warm,  because  the  blood  circulates  more  rapidly 
in  the  superficial  portions  of  the  body — as  the  skin,  and  then  an 
effect  is  produced  upon  the  nerves  which  supply  those  parts, 
and  a  corresponding  sensation  developed.  This  is  very  nicely 
shown  in  ague.  Here  there  are  shivering  and  perspiring  fits  alter- 
nating with  each  other.  In  both  the  temperature  of  the  blood  is 
proved  to  be  the  same  by  the  application  of  the  thermometer  •  but 
when  the  patient  complains  of  the  intense  cold,  and  the  trembling 
movements  characteristic  of  the  disease  come  on,  then  it  is  found  that 
the  blood  has  left  the  surface,  and  the  internal  organs  are  overloaded 
with  it ;  whilst  on  the  other  hand,  when  the  flushing  and  perspiring 
attack  makes  its  appearance,  the  vital  fluid  has  returned  in  unusual 
proportion  to  the  skin,  and  has  left  the  viscera.  This  demonstrates 
conclusively  that  the  sensations  of  heat  and  cold  do  not  prove  that 
actually  the  temperature  of  the  body  has  been  altered.  Therefore,  it 
is  quite  clear  that  few  persons  know  what  heat  is  ;  and  many^ill  be 
surprised  to  learn  that  what  they  understand  by  the  term  is  little 
more  than  a  name  which  is  given  to  one  of  the  effects  of  heat.  Heat 

is  really but,  stay !  What  is  this  ?  "  All  persons  trespassing 

on  these  grounds  will  be  prosecuted."  Why,  dear  me !  Where  are 
we  ?  Oh,  I  see  !  Professor  Faraday's  domain.  Let  us  retrace  our 
steps  as  quickly  as  possible ;  for  if  we  ventured  any  further  it  would 
not  be  to  our  advantage. 

I  was  saying  that  man's  blood  is  always  maintained  during 
life  at  a  temperature  of  98  deg. ;  the  question  then  arises,  how 
is  this  effected?  Heat  is  derived  from  two  sources*;  the  sun, 
and  chemical  combination.  The  second  you  may  not  at  first  recog- 
nize ;  it  is  the  mode  in  which  heat  is  produced  by  an  ordinary  fire. 
For  example :  the  carbon  of  the  coal  unites  with  the  oxygen  of  the 
air,  and  forms  heat  and  flame,  the  smoke  being  composed  of  minute 
particles  of  the  carbon  which  have  not  been  quite  burnt,  and  which 
therefore  are  so  much  valuable  material  expended  uselessly. 

*  It  is  possible  that  heat  of  all  kinds  is  only  physical  motion  of 
minute  pai~ticles  of  matter,  even  that  the  heat  of  the  sun  is  due  to  the  effect 
of  its  attraction  of  the  atoms  of  atmospheric  air ;  but  the  old  view  is  the 
more  intelligible  to  ordinary  readers. 


92  POPULAR  PHYSIOLOGY. 

Can  we  now  apply  this  theory  of  the  production  of  heat  to  explain 
the  process  in  the  human  body  ?  Yes,  in  some  measure ;  but  we 
must  not  imagine  that  all  the  heat  of  our  blood  results  from  any  kind 
of  combustion.  Many  years  ago  a  great  French  chemist  put  forward 
the  view  that  the  temperature  of  the  body  was  due  to  combustion : 
in  fact,  that  the  carbon  of  the  blood  joined  the  oxygen  of  the  air,  ana 
developed  heat,  this  phenomenon  taking  place  in  the  lungs.  I  here 
anticipate  a  question  you  are  about  to  ask,  by  telling  you  that  com- 
bustion may  take  place,  and  heat  may  be  formed,  without  flame.  The 
manure  in  a  dung- pit  is  very  warm,  the  heap  of  leaves  in  the  adjoining 
grove,  which  the  cruel  winds  of  autumn  have  severed  from  their  parent 
branchlets,  and  which  we  turn  over  with  our  walking-stick  as  we  pass 
along,  are  reeking  hot.  See  how  yonder  hay-rick  steams !  Thrust  your 
hand  into  its  side,  and  feel  the  scalding  temperature  of  its  interior, 
and  then  say  there  cannot  be  heat  without  flame.  In  all  the  instances 
I  have  alluded  to,  combustion  has  been  taking  place,  and  the  carbon, 
whether  in  the  dung-hill,  the  leaf  heap,  or  the  hay-rick,  is  slowly 
but  certainly  uniting  with  the  atmospheric  oxygen. 

So  you  see  there  was  some  reason  in  this  doctrine,  that  the  lungs 
were  the  furnace  of  the  body;  and  popular  lecturers  were  wont  to  say 
that  the  ribs  were  the  bars  of  the  grate,  and  the  diaphragm  the  huge 
forge-bellows,  which  propelled  the  air  through  the  burning  fuel. 
This  was  all  very  nice,  and  exceedingly  simple ;  but,  alas !  like  all 
exceedingly  *  nice  theories  was  destined  to  succumb  to  science. 
Unhappily  for  this  idea,  it  was  found— firstly,  that  the  furnace  was 
no  hotter  than  the  water  tubes  which  carried  the  heat— that  the 
temperatures  of  the  lungs  and  the  little  toe  were  identical ;  and 
secondly,  that  the  quantity  of  carbonic  acid  generated  was,  occasion- 
ally, much  greater  than  could  have  been  formed  from  the  amount  of 
oxygen  taken  in  by  the  lungs.  Advancing  science  tolled  the  curfew, 
and  out  went  the  lung-fire  theory,  never  to  be  rekindled. 

From  its  ashes  there  sprang,  Phoenix-like,  a  second  hypothesis— 
that  of  Liebig.  This  philosopher  contended  that,  though  combustion 
did  not  take  place  in  the  lungs,  yet  that  certain  alimentary  materials 
were  really  burnt  in  the  capillaries  distributed  throughout  the  body. 
In  carrying  out  his  opinion  he  divided  all  sorts  of  food  into  two  classes. 

|  Heat  producers 
Food    - 

I  Flesh  producers 

On  the  supposition  that  all  the  aliments  of  the  second  group  went  to 
build  up  the  worn-out  tissues,  and  all  the  others  to  maintain  the 
animal  heat. 

*  I  need  not  here  call  attention  to  the  contest  now  taking  place  between 
the  advocates  of  creation-of-species-ism,  and  those  who  support  the  grand 
generalization  of  Mr.  Darwin. 


SOUKCES  OF  ANIMAL  HEAT.  93 

According  to  this  view,  we  should  regard  the  microscopic  blood- 
vessels of  the  whole  body  as  collectively  constituting  a  sort  of  oil  or 
spirit  lamp,  in  which  are  burnt  the  fatty  and  alcoholic  portions  of  the 
food,  combining  here  with  the  oxygen  introduced  into  the  arterial 
blood  through  the  medium  of  the  lungs.    It  is  a  hypothesis  in  part 
correct,  and,  to  some  extent,  erroneous ;  for,  as  1  observed  in  an 
earlier  chapter,  we  must  not  think  that  the  only  office  of  the  oily  and 
starchy  portions  of  the  food  is  to  keep  up  heat,  because  they  also 
enter  into  the  composition  of  the  tissues  ;  and  furthermore,  we  know 
that  heat  is  produced  apart  from  the  combustion  of  food.    When 
a  mixture  is  made  of  oil  of  vitriol  and  water,  a  very  intense  heat  is 
formed,  and  the  same  thing  holds  good  for  many  other  mixtures. 
When  salts  of  various  descriptions  are  decomposed,  or  caused  to 
unite  with  each  other,  the  temperature  is  increased ;  and  since  we 
know  that  hundreds  of  such  changes  are  being  made  in  the  animal 
body  during  everv  moment  of  our  lives,  we  have  here  sufficient  proof 
that  food  is  not  tne  only  agent  in  the  production  of  warmth.    Again, 
it  has  been  shown  that  when  animals  were  fed  upon  food  which  con- 
tains neither  fats  nor  starch,  the  heat  of  the  frame  was,  nevertheless, 
kept  up.    Plants  which,  in  the  daylight,  do  not  cause  carbon  and 
oxygen  to  unite,  but  even  separate  them  from  one  another,  possess 
heat  to  a  certain  extent;  whilst,  during  the  night,  when  their  carbon 
combines  with  the  oxygen,  forming  carbonic  acid,  as  in  the  case  of 
man,  the  quantity  of  heat  generated  is  much  less  than  that  formed 
under  the  influence  of  the  sun ;  and  for  this  reason,  during  the  day, 
the  different  processes  of  repair  are  going  on  with  rapidity;  but 
during  the  night  they  are  almost  quiescent.    A  favourite  argument 
of  those  who  would  have  us  put  our  trust  in  Liebig's  doctrine,  is  one 
deduced  from  certain  experiments  on  pigeons.    These  birds  were 
kept  fasting,  and  it  was  remarked  that  the  temperature  fell  very 
much-    hence  the  conclusion  that  food  is  the  generator  of  heat. 
This,  nowever,  is  only  special  pleading,  for  after  some  days  of  starva- 
tion, the  temperature  of  the  pigeons  rose  again ;  thus,  more  effectu- 
ally than  ever,  putting  the  extinguisher  on  Liebig's  supposition  that 
fats,  starch,  and  such  like,  are  the  sole  source  of  animal  heat. 

Eriction  gives  rise  to  increase  of  temperature.  Rub  two  pieces  of 
board  together,  and  mark  the  heat  produced ;  or  pull  a  cord  rapidly 
backwards  and  forwards  over  a  rough  surface,  and  observe  how  hot 
it  will  become.  We  can  fairly  presume  that  warmth  is  developed  in 
the  blood-vessels  in  a  somewhat  similar  way :  firstly,  by  the  velocity 
with  which  the  stream  of  fluid  is  driven  through  the  vessels ;  and 
secondly,  by  the  friction  or  rubbing  of  the  blood  disks  against  each 
other.  In  summing  up,  we  may  assert  that  the  heat  of  the  body  is 
derived  from  three  distinct  sources  : — 

1st. — The  combustion  of  certain  portions  of  the  food. 
2nd. — The  combination  and  decomposition  of  different  tissue 
materials. 

Qrd TV.P  fr1vf  :„„  /  a  Between  the  blood  and  sides  of  vessels. 

drd.    Ihe  friction  { b  Between  the  blood  disks  themselves. 


94  POPULAE,  PHYSIOLOGY. 

Some  parts  of  the  nervous  system  appear  to  exert  great  control 
over  the  temperature  of  the  body.  These  portions  are,  collectively, 
called  the  sympathetic  nervous  system  ;  and  such  is  its  influence  that 
if  the  branch  of  either  side  be  divided,  it  is  found  that  the  regions 
supplied  with  filaments  from  it  have  their  temperature  greatly  in- 
creased. This  alteration  is  thus  accounted  for  :  the  capillaries  are 
provided  with  two  sets  of  nerves,  whose  actions  are  antagonistic ;  the 
sympathetic  nerve,  by  acting  on  the  coats  of  the  vessels,  tends 
to  lessen  their  calibre,  and  the  ordinary  nerves  operate  in  such  a  way 
as  to  cause  an  increase  of  this  latter.  When  the  sympathetic  is  cut 
its  influence  ceases,  and  then  the  ordinary  nerves,  by  virtue  of  their 
opposite  power,  cause  the  canals  to  expand.  When  the  vessel  is 
enlarged,  it  contains  a  greater  quantity  of  blood  than  usual ;  hence 
there  is  a  greater  amount  of  chemical  change  and  more  friction, 
and,  therefore,  an  increase  of  temperature,  which  increase  often 
reaches  to  as  much  as  eleven  degrees  above  tne  ordinary  heat. 

It  is  exceedingly  interesting  to  mark  the  difference  between  the 
higher  and  lower  animals  regarding  the  effects  upon  them  of  diminu- 
tion of  temperature.  Tor  example,  while  we  can  freeze  the  grubs  of 
certain  moths  without  injury  or  destruction  to  life,  if  we  lower  the 
temperature  of  man's  blood  to  sixty-eight  degrees  he  ceases  to  exist. 
In  one  instance,  the  larva  of  an  insect  had  been  so  completely  frozen 
that  when  thrown  into  a  glass  vessel  it  "  chinked,"  as  a  stone  would, 
yet,  when  heat  was  applied,  life  was  restored,  and  after  the  proper 
interval  the  maggot  became  a  perfect  moth. 

If  the  blood  of  man  be  elevated  about  thirteen  degrees  above  the 
natural  temperature,  life  is  extinguished,  although  you  can  virtually 
boil  some  of  the  lower  creatures  (wheel-animalcules)  without  de- 
stroying vitality.  You  may  possibly  ask,  If  this  be  the  case,  how 
can  a  person  enter  an  oven,  heated  to  500  or  600  degrees,  without 
sustaining  any  injury  ? — a  feat  which  has  been  over  and  over  achieved 
by  "The  Fire  King/'  Chabert,  and  others.  The  reply  to  this  I 
must  defer  to  the  next  chapter,  as  it  involves  a  reference  to  the 
organs  situate  in  the  skin,  and  to  the  effects  of  heat  on  water,  of 
which  we  have,  up  to  this,  said  nothing. 


THE   SKIN. 


95 


CHAPTER    X. 

The  Skin — Epidermis  or  Cuticle,  and  Derma — Corns — Structure  of  the 
Papillse — Perspiration — Form  and  number  of  Sweat-glands — Twenty- 
seven  miles  of  Perspiration  Tubing — Composition  of  the  Perspiratory 
Fluid — End  attained  by  the  action  of  the  Sweat-glands — Injurious 
effect  of  Lactic  Acid  when  retained  in  the  system — Experiments  on 
Dogs — How  the  temperature  of  the  Blood  does  not  exceed  98°  Faht. — 
Why  a  man  can  enter  with  impunity  an  Oven  heated  to  600° — Impro- 
priety of  employing  the  expression  Latent  Heat — Transportation  of 
Force  when  Solids  pass  into  Liquids,  and  the  latter  into  Gases. 

THE  skin  is  the  tissue,  or  membrane,  -which  clothes  the  surface  of 
the  body  externally,  and  is  composed  of  two  layers,  an  inner  and  an 
outer,  separated  by  a  thin  bed  of  gelatinous  substance.  Let  us 
take  a  thin  slice  of  it,  and  place  it  beneath  the  microscope !  We  per- 
ceive that  one  side  of  the  specimen  is  com- 
posed of  a  vast  number  of  interlacing  cords,  or 
bands,  which  end  in  a  dark  space,  and  on  the 
other  side  of  this  we  see  several  rows  of  par- 
ticles, the  first  of  which  are  somewhat  oval,  but 
these  as  we  advance  become  spindled-shaped, 
and  the  outer  ones  are  quite  scaly— three  or 
four  being  united,  and  flattened  out.  We  also 
observe  that  the  intervening  dark  line  is 
thrown  into  a  number  of  wave-like  folds,  to 
which  the  first  row  of  particles  conforms. 
The  outer  stratum  is  called  the  epidermis, 
or  cuticle  (a),  the  inner  the  derma  (b),  and 
both  grow  from  the  dark  line, — the  oldest 
part  of  the  first  being  the  outer,  and  of  the 
second  the  inner  surface  (fig.  49).  There 
are  no  blood-vessels  in  the  epidermis,  and 
this  is  the  reason  why  a  person  may  pare  a 
corn,  or  cut  an  old  blister,  without  bleeding 
from  the  parts  so  operated  on.  Its  only 
object  is  to  protect  the  important  tissue 
beneath,  and  it  has  a  peculiar  power  of  grow- 
ing fastest  where  most  pressed  on,  as  if  nature 
foresaw  the  necessity  and  made  the  provision. 
Therefore  we  find  the  hands  and  feet  protected 
by  very  thick  layers  of  cuticle,  whilst  on  other 
parts,  as  the  lips  and  cheeks,  it  is  extremely  de- 
licate. But,  as  any  good  quality  may  by  a  com- 
bination of  circumstances  be  converted  into 
evil  one,  so  is  this  power  of  the  outer 


an  evil  one,  so  is  this  power  ot  the  outer  Fig.  49. 

skin  to    grow  quickest  where  there  is  most 

pressure,  in  many  instances  an  exceedingly  unsatisfactory  one. 


Can 


96 


POPULAR  PHYSIOLOGY. 


you  ask  why  ?  Because,  were  it  not  for  this  property  we  should 
never  be  plagued  with  corns, — kinds  of  growth  due  entirely  to  the 
development  of  the  epidermis,  which  is  set  a  thickening  by  the 
squeezing  of  a  cruel  boot. 

Beneath  the  skin  lie  the  myriads  of  microscopic  blood-vessels 
that  give  the  body  the  peculiar  colour  which  is  absent  after  death. 
Along  with  them  are  placed  the  branches  of  the  nerves,  which  endow 
the  surface  with  the  capability  of  receiving  impressions.  These 
nerves  proceed  outward  as  far  as  the  derma,  but  go  no  further ;  and, 
as  we  shall  see  presently,  they  in  many  instances  terminate  in  little 
elliptical  bodies.  Mark  the  hundreds  of  small  furrows  upon  the 
under  parts  of  your  fingers.  These,  no  doubt,  have  been  often 
observed  by  you  with  the  aid  of  a  magnifying  lens ;  but  do  you 
know  what  they  are  for?  No.  Well,  let  us  first  see  how  they  are 
produced  and  then  consider  their  purpose.  You  saw  in  the  section 
placed  beneath  the  microscope,  a  series  of  elevations  alternating 
with  depressions.  The  projecting  hillocks  are  termed  papillae,  arid 
these  in  great  numbers  make  up  the  lines  upon  your  fingers,  in  which 
lines  the  sense  of  touch  resides. 

In  each  papilla  is  found  a  very  minute,  pea-shaped,  solid  body, 
round  which  a  nerve  passes,  or  into  which  it  enters.  When  the 
finger  is  pressed  against  anything  this  little  organ  is  displaced  to 
some  extent,  and  the  effect  produced  on  the  nerve  is  then  con- 
veyed to  the  brain,  giving  rise  to  an  idea  or  conception.  Of  these, 
more  in  another  chapter. 

Embedded  in  the  deeper  layers  of  the  skin  are  many  organs  of 
minute  size,  called  the  sweat-glands.  These  are  of  two  kinds :  the 
first  secrete  a  sort  of  waxy  fluid,  and  are  found 
well  developed  in  the  tube  of  the  ear  ;  the  second 
are  the  most  important,  for,  when  taken  together, 
they  form  an  organ  of  a  much  more  influential 
character  than  the  kidneys  themselves.  It  is  a 
matter  of  no  great  difficulty  to  prepare  a  portion 
of  skin  containing  one  of  these  glands,  and  there- 
fore you  will  suppose  when  looking  at  the  diagram 
(fig.  49),  that  you  are  peeping  through  the  micro- 
scope at  the  section  I  have  prepared.  Each  of 
these  organs  consists  of  a  tube,  whose  only  opening 
is  external,  and  which  traverses  the  entire  skin 
from  its  deepest  to  its  most  superficial  portion. 
This  tube  or  canal  is  twisted  into  a  knot  below  (fig. 
50),  and  lies  in  a  little  sac,  which  is  surrounded  by 
blood-vessels.  For  the  rest  of  its  course  it  wends 
its  way  in  slight  curves  till  it  reaches  the  surface 
of  the  body,  where  its  opening  is  situate.  The 
sweat,  or  perspiration,  which  it  is  the  office  of  these  glands 
to  form,  is  drawn  into  their  knotted  ends  from  the  adjacent  blood- 
vessels, and  travels  along  the  tubes  till  thrown  out  upon  the 
skin.  The  number  of  sweat-glands  is  astounding,  and  ought  to 
afford  us  some  estimate  of  the  necessity  for  attending  to  the  state  of 


Fig.  50. 


THE  PEKSPIEATION.  97 

the  skin.  It  has  been  calculated  by  an  English  anatomist,  that  in  every 
square  inch  of  the  skin  there  are  at  least  2800  of  these  glands,  and 
as  there  are  in  a  person  of  ordinary  size  at  least  2500  square  inches 
of  surface,  it  follows  that  the  entire  number  of  sweat-glands  is  seven 
millions. 

Now,  every  gland  tube  when  straightened  measures  a  quarter  of 
an  inch  in  length,  _and  this  divided  into  the  total  number  of  glands 
will  give  (supposing  the  tubes  arranged  end  to  end)  a  length  of 
tubing  of  1,750,000  inches,  or  145,833  feet,  or  48,611  yards— or  more 
than  twenty-seven  miles, — a  system  of  sewage,  beside  which  that  of 
some  of  our  cities  sinks  into  insignificance.  The  perspiration  fluid  is 
of  a  sour  character,  and  contains  a  certain  proportion  of  lactic  acid,* 
some  organic  matter,  and  various  salts.  It  is  constantly  secreted, 
although  we  only  perceive  it  when  in  large  quantities,— as  after  much 
exercise.  The  average  daily  amount  formed  is  one  pound  six  ounces, 
but  as  it  depends  upon  the  extent  to  which  the  muscles  have  been 
exerted,  it  is  hard  to  fix  the  exact  quantity.  By  means  of  the  per- 
spiration, three  ends  are  attained — 

1st.  The  blood  is  concentrated. 
2nd.  An  acid  is  got  rid  of. 
3rd.   The  body  is  kept  cool. 

Of  course  you  see  the  way  in  which  the  first  is  achieved.  The 
water  is  prevented  accumulating  by  being  got  rid  of  in  the  sweat. 
If  it  remained,  the  fluid  would  distend  the  capillaries,  and  at  length 
force  its  way  from  them  under  the  skin,  producing  general  dropsy ; 
and  this  is  the  reason  why,  in  such  a  disease,  physicians  prescribe 
remedies  which,  by  acting  on  the  glands  of  the  skin,  cause  them  to 
abstract  the  watery  element  of  the  blood.  This,  then,  in  its  turn 
absorbs  the  fluid,  which  had  made  its  escape  under  the  integument, 
and  so  the  parts  are  restored  to  their  natural  condition. 

It  is  of  the  greatest  importance  that  this  lactic  acid,  to  which  I 
have  alluded,  be  expelled  from  the  system,  for  when  retained  it 
causes  that  most  troublesome  of  maladies — rheumatism.  Therefore, 
it  should  be  remembered  that  constant  exercise  is  one  of  the  preven- 
tives of  this  disease ;  the  exertion  causes  a  flow  of  perspiration,  in 
which ^the  acid  is  poured  out.  It  might,  at  first  sight,  appear  an 
objection  to  this  view,  that  even  farm  labourers  are  sometimes 
attacked  by  "  the  rheumatics ;"  but  so  far  from  upsetting  the  doctrine, 
it  really  supports  it,  as  thus :  A  man  who  works  much  (physically) 
develops  a  greater  amount  of  lactic  acid  than  one  whose  occupation 
is  of  a  sedentary  nature ;  therefore  any  check  to  its  removal  will 
exhibit  itself  more  fully  in  the  former  than  in  the  latter.  This  check 
is  produced  by  an  exposure  to  cold,  which  brings  down  the  tempera- 
ture of  the  surface,  and  so  prevents  the  formation  of  the  sweat. 
When  lactic  acid  was  injected  into  the  veins  of  dogs  and  cats, 
these  animals  were  almost  immediately  affected  with  rheuma- 
tism ;  and  when  a  post-mortem  examination  was  made,  the  internal 

*   The  acid  of  sour  milk. 
II 


98  POPULAR  PHYSIOLOGY. 

marks  were  the  same  as  those  in  men  who  had  died  of  rheumatic 
disease — a  fact  which  demonstrates  very  fully  the  cause  of  this 
horrible  ailment. 

The  third  function  of  the  perspiration  glands  touches  on  one  of 
the  most  interesting  series  of  phenomena  in  the  whole  category  of 
vital  actions.  It  is  familiar  to  every  one  that  when  much  muscular 
exertion  has  been  made,  the  body  becomes  excessively  warm ;  there 
is  an  increased  flow  of  liquid  from  the  skin,  and  the  breath  is  quick- 
ened, as  well  as  the  pulse.  Why  do  all  these  changes  take  place  ? 
We  shall  consider  them  one  by  one.  When  the  muscles  are  employed, 
as  in  any  violent  exertion,  they  undergo  extensive  waste ;  this  in- 
volves as  extensive  repair,  and  as  the  reparative  materials  are  derived 
from  the  blood,  it  (by  the  form  of  attraction  to  which  I  have  directed 
attention  elsewhere)  is  drawn  more  ramdly  towards  them  than  before, 
so  that  the  circulation  is  accelerated  ;  out  its  velocity  is  also  increased 
by  the  pressure  of  the  muscles  on  the  veins  which  carry  the  fluid  to 
the  heart.  In  this  way  the  beats  of  the  pulse  and  heart  are  more 
numerous  per  minute.  The  blood  being  brought  more  swiftly  to  the 
lungs  than  hitherto,  the  chest  is  stimulated ;  the  air  is  then  drawn  in, 
in  order  to  purify  the  circulating  fluid,  and  by  allowing  it  to  pass 
away,  to  make  room  for  that  behind.  Therefore  the  inspirations  and 
expirations  are  more  frequent.  Greater  heat  is  produced,  because  of 
the  increased  chemical  change  going  on  in  the  muscles,  which  are 
being  momentarily  repaired,  and  deprived  of  refuse  materials,  thus 
involving  a  series  of  combinations  ana  decomposition  of  certain  animal 
principles,  which,  as  I  have  shown,  raise  the  previous  temperature. 

The  next  Question  is,  How  is  it  that  perspiration  ensues  ? — 1st. 
Because  the  blood-vessels  wliich  bring  the  nutritive  materials  to 
the  muscles  are  also  those  which  send  branches  around  the  knotted  ends 
of  the  glands ;  as  the  circulation  of  blood  in  the  former  canals  is  acce- 
lerated, so  is  it  in  the  latter,  and  the  sweat  organs  being  supplied  in 
a  given  time  with  a  greater  quantity  of  blood,  will  secrete  a  propor- 
tionate amount  of  perspiration  liquid ;  and  2ndly,  Because  during 
muscular  exertion  more  than  the  ordinary  supply  of  lactic  acid  is 
generated ;  and  as  it  is  the  province  of  these  glandules  to  expel  this 
substance  from  the  system,  they  are  thus  urged  to  secrete  more 
quickly  than  whilst  the  individual  was  at  rest. 

Now  the  above  sketch  brings  us  to  the  consideration  of  what  we 
put  off  in  the  last  chapter,  viz. : — the  reason  why  (although  the  tem- 
perature of  the  blood  cannot  be  raised  to  111°)  a  man  can  enter  an 
oven  heated  to  500°  or  600°  with  impunity. 

When  by  the  action  of  heat  a  solid  is  converted  into  a  liquid,  as 
ice  into  water ;  or  a  liquid  is  changed  into  a  vapour,  as  water  into 
steam,  a  certain  quantity  of  the  heat  employed  vanishes  apparently. 

If,  for  example,  you  apply  the  flame  of  a  spirit-lamp  to  a  vessel 
containing  water,  it  will,  after  a  while,  boil,  that  is,  it  will  reach  a 
temperature  of  212° ;  but  no  furnace,  not  even  that  of  the  great 
Jewish  king,  could  enable  you  to  raise  it  one  degree  higher,  so  long 
as  the  steam  could  pass  away.  _  You  see,  then,  that  when  water  passes 
into  the  state  of  vapour,  heat  is  lost  (?).  We  can  hardly  say  it  is  lost; 


CORRELATION  OF  HEAT  AND  MECHANICAL  FORCE.  99 

for,  if  we  bring  the  steam  or  vapour  back  again  to  the  condition  of  a 
liquid,  the  heat  is  experienced.  Natural  philosophers  have  given  the 
term  latent  (hidden)  to  this  quantity  of  caloric,  which  was  so  disguised 
that  they  could  not  detect  it.  But  this  is  no  explanation.  The  true 
cause  is  this :  heat  is  not  a  distinct  force,  but  only  a  form  of  the  one 
force  which  exists  all  through  nature,  ana  which,  when  water  is  being 
changed  to  steam,  is  metamorphosed,  or  converted  into  mechanical 
power.  Water  cannot  expand  except  when  vaporised ;  it  is  vaporised 
by  heat,  which  in  this  way  gives  birth  to  mechanical  power. 

Pardon  this  digression.  Suffice  it  to  say,  that  when  liquid  passes 
into  steam,  heat  is  lost.  Now  water  can  pass  into  vapour  at  the  tem- 
perature of  the  body,  and  in  doing  so  robs  the  body  of  its  heat. 
This,  then,  is  the  mode  in  which  the  temperature  of  the  body  is  kept 
at  its  normal  standard.  When  a  man  enters  an  almost  fiery  oven, 
perspiration  is  formed  very -copiously ;  this,  by  the  temperature  of 
the  surrounding  air,  is  vaporised  as  fast  as  it  is  secreted,  and  the 
surface  of  the  skin  is  found  nearly  as  cool  as  before.  If,  however,  the 
air  of  the  oven  were  so  charged  with  moisture,  that  it  could  contain 
no  more  (and,  therefore,  that  no  conversion  of  the  perspiration  into 
steam  could  result),  then  the  temperature  of  the  skin  would  be 
intolerable,  and  the  individual  exposed  to  it  would  literally  be  scalded 
to  death. 

It  is  on  this  account  also,  that  on  a  day  when  the  atmosphere  is 
overloaded  with  moisture,  we  can  take  little  exercise  without  being 
covered  with  perspiration  which  has  not  been  vaporised,  and  that  we 
complain  of  oppressiveness,  &c.  For  this  reason,  too,  we  find  the 
habit  of  wearing  waterproof  clothing  so  unpleasant  —  the  secreted 
fluid  being  retained  warm  upon  the  surface  of  the  skin,  and  not  con- 
verted into  vapour  as  it  should  be.  Pour  into  the  palm  of  one  hand 
a  little  oil,  and  into  that  of  the  other  some  ether,  and  observe  the 
difference  in  the  sensations  produced.  The  oil  will  not  be  vaporised, 
and  will  not  chill  the  hand ;  the  ether,  on  the  contrary,  will  disappear 
in  a  moment,  leaving  such  a  feeling  of  cold  as  might  be  produced  by 
holding  a  piece  of  ice.  I  fancy  you  are  now  in  a  fair  position  to 

frasp  the  idea.  What  a  beautiful  chain  of  phenomena  is  that  exhi- 
ited  whilst  we  are  taking  our  routine  walk  of  an  afternoon.  Now 
that  we  have  unravelled  the  coil,  and  examined  the  different  links  of 
cause  and  effect  which  compose  it,  how  infinitely  intelligent  seems 
the  foresight  which  provided  such  admirable  means  and  appliances 
for  securing  our  happiness  and  comfort.  Oh !  if  men  would  only 
reflect  upon  the  wondrous  power  of  the  Creator,  as  shown  in  their 
very  selves,  and  would  inwardly  confess  His  majesty  and  beneficence, 
is  it  not  probable  that  a  more  gratifying  offering  would  thus  be  pre- 
sented than  in  many  of  the  empty  conventional  mockeries  by  which  we 
deceive  ourselves  in  an  endeavour  to  defraud  Heaven. 

"  Lo  !  the  poor  Indian,  whose  untutor'd  mind 
Sees  God  in  clouds,  and  hears  Him  in  the  wind." 


100 


POPULAK  PHYSIOLOGY. 


CHAPTER    XL 

The  Kidneys,  their  general  and  microscopic  Anatomy — What  they  do, 
and  how  they  do  it — Composition  of  their  Secretion — The  Solid  and 
Liquid  constituents  formed  in  separate  Localities — Pyropathy  and  the 
Turkish  Bath— The  latter  calculated  to  increase  the  per-centage  of 
Heart  and  Kidney  Diseases — Action  of  the  Hot-air  Bath  on  the  Circu- 
lation is  by  woweemsanalagousto  that  of  Muscular  Exertion — Decrease 
in  the  Liquid  Elements  of  the  Blood  by  increased  action  of  the  Sweat- 
glands  tends  to  bring  about  "Stone" — Arguments  in  support  of  the 
Turkish-bath— The  Spleen— Thyroid— Thy mus— Function  of  the 
Spleen. 

DURING  our  wanderings  in  the  human  world  through  which  we 
have  travelled  so  far  together,  we  did  not  come  across  the  regions 
known  as  the  kidneys.  We  have  now,  however,  arrived  at  them,  and 
mean  to  inquire  n9t  only  into  their  geo- 
graphy, but  into  their  condition  as  a  manu- 
facturing colony  also. 

Where  do  they  lie  ?  On  each  side  of  the 
backbone,  being  a  few  inches  distant  from 
it,  and  a  little  below  the  ribs.  It  seems 
almost  absurd-  to  say  that  they  are  shaped 
like  a  kidney-bean,  yet  such  is  the  descrip- 
tion usually  given  in  anatomical  works.  If 
I  were  to  give  their  minute  characters  of 
form,  it  would  puzzle  more  than  please ;  and 
as  I  am  sure  most  of  my  readers  are  ac- 
quainted with  the  features  of  a  "mutton 
kidney  "  in  the  undeyilled  state,  as  well  as 
in  the  more  interesting  condition,  I  need 
only  say  that  in  form  the  human  one  is 
exactly  the  same  as  that  of  the  sheep.  It 
weighs  about  four  ounces.  So  that  he  who 
has  eaten  four  for  supper  may  be  fairly  said 
to  have  had  "  his  pound  of  flesh,"  though 
no  ^|/lock.  I  take  a  double-bladed  knife, 
and  with  it  cut  a  thin  section  of  the  gland, 
moving  the  instrument  in  one  direction  only, 
from  the  curved  or  outer  part  of  the  kidney  to 
the  inner  or  notched  one  (fig.  51).  Now,  we 
have  laid  out  the  slice  on  a  plate  of  glass, 
and  observe  that  the  internal  portion  is  an 

and  d   the  tubular    empty  ^^  ^  ending  ^  ft   membranous 

canal  (£),  whilst  the  outer  or  convex  part 
is  of  a  fleshy  appearance.  On  looking  at  it  with  a  magnifying 
lens,  however,  we  detect  a  difference  between  the  outside  and 


Fig:.  51  —  Granular  and 
tubular  portions  of  the 
Kidney,  in  the  upper  figure 
diminished,  c,  the  gra- 


MICROSCOPIC  ANATOMY  OF  KIDNEY. 


101 


inside  of  this  mass 
of  tissue, — the  first 
appearing  granular 
(e),  the  second  as 
if  made  up  of  tubes 
(d);  and  further- 
more we  behold  se- 
veral small  arteries 
making  their  way 
outwards,  and  di- 
viding, and  forming 
knots  in  the  granu- 
lar division.  Next, 
we  remove  a  little 
piece  of  this  slice, 
and  placing  it  be- 
tween two  slips  of 
glass,  lay  it  on  the 
stage  of  our  micro- 
scope, and  scruti- 
nise it  more  closely 
than  before.  We 
are  well  repaid  for 
our  trouble,  for  now 
the  entire  structure 
of  the  organ  unfolds 
itself  to  the  eye  (fig. 
52). 

We  see  hundreds 
of  beautiful  trans- 
parent tubes  (d,  d), 
expanding  at  their 
extremities  into  little  grape- 
like  balls  (a,  a),  into  each  of 
which  a  minute  artery  (b,  bj 
enters,  forming  a  knotted  tuft 
within,  and    from  which    a 
smaller  vein  departs. 

Let  us  follow  this  vein  (fig. 
53).  We  see ittravelling down 
by  the  side  of  9110  of  the  tubes, 
and  then  dividing  and  sub- 
dividing, and  joining  with 
others,  till  at  length  an  ex- 
quisite network  of  vessels  is 
produced— an  entanglement 
of  meshes— closely  surround- 
ing the  tube.  Glancing  still 
lower  (or  more  internally) 
the  tube  is  seen,  after  unit- 


102  POPULAR  PHYSIOLOGY. 

ing  with  others,  to  end  by  an  open  mouth  in  the  empty  space 
which  the  kidney  contains. 

The  membranous  canal  that  we  saw  emerging  from  the  notched 
border  is  continued  onward  from  each  kidney,  behind  the  intestines, 
to  a  sac  or  resevoir  which  is  situate  in  the  lower  part  of  the  abdomen, 
and  which  in  common  parlance  is  styled  the  bladder  (fig.  54). 

Grape-like  Vesicle. 


Net-tvork. 


Fig.  53 . 

The  duty  of  the  kidneys  is  to  separate  a  liquid  (the  urine)  from 
the  blood,  and  this  liquid  when  formed  is  carried  by  the  two  canals 
to  which  I  have  referred,  to  the  bladder ;  thence,  after  a  period,  to  be 
expelled  from  the  body.  m 

What  is  the  signification  of  all  the  strange  arrangements  we  have 
been  examining  with  the  aid  of  the  microscope  ?  It  is  necessary 
before  replying  to  this  question  to  let  you  know  something  of 
the  manufactured  compound,  before  reviewing  the  processes  by 
which  it  is  prepared. 

This  liquid  is  composed  of  water,  holding  various  salts  in  solution, 
which  when  imperfectly  dissolved  give  rise  to  the  painful  disease, 
p ravel— or  may  eventually  develop  calculus  or  stone.  That  beneath 
is  the  stereotyped  composition  : — 

"Water     . .     . .     938  \ 

A  peculiar  organic  substance,  urea  30  I  •    inm  „._ 

Salts  of  potash,  soda,  ammonia,  1  m  1(  )0  Parts' 

lime,  and  magnesia       . .     . .  5  32  / 

£5)0 

Bear  well  in  mind  the  position  of  the  different  structures,  and  you 
can  attend  to  the  account  of  the  formation  of  the  kidney  secretion. 
The  urea  and  the  salts  transude  through  the  veins  into  the  lower 
portion  of  the  tubes,  in  fact  they  ooze  through  ;  but,  on  their 
entrance,  they  are  in  too  concentrated  a  form  to  travel  any  further, 
otherwise,  as  you  were  doubtless  about  to  say,  they  would  pass  into 


INFLUENCE  OF  THE  TURKISH  BATH.  103 

the  empty  space,  and  finally  into  the  bladder.  How  then  is  their 
future  passage  provided  for  ?  The  watery  element  of  the  blood  is- 
allowed  to  flow  from  the  little  tuft  of  arteries  contained  in  the  grape- 
like  expansion  of  the  tube,  and,  as  it  has  to  reach  the  empty  space 
also,  it  naturally  pushes  before  it  the  crowd  of  idle  bystanders  wnich 
blocked  up  the  thoroughfare,  just  as  the  stream  of  water  from  a  stop- 
cock drives  before  it  the  particles  of  filthy  matter  in  a  sink  or  wash- 
hand  basin.  What  an  admirable  contrivance,  and  how  wonderfully 
the  means  are  adapted  to  the  end !  Oh,  Nephrophagous*  gourmand, 
you  whose  pleasure  it  is  masticate  the  renal  organs  of  the  ovine 
genus,  yea,  even  in  their  most  diabolical  condition,  how  little  do  you 
think  of  the  thousands  of  small  bodies  you  are  dooming  to  destruc- 
tion with  that  remorseless  jaw-bone  of  yours ! 

This  is  the  place  to  give,  as  Edward  Forbes  would  have  said,  "  a 
screed  anent  "  the  Turkish  bath,  and  its  effects  upon  the  system.  I 
take  it  for  granted  that  you  know  what  a  Turkish  bath  is;  for, 
"breathes  there  a  man"  who  has  not  heard  of  Holloway's  pills, 
Du  Barry's  Reyalenta  Arabica,  and  Mr.  Barter's  public  stewing  appa- 
ratus, f  I  am  inclined  to  think  that  one  of  the  most  praiseworthy  fea- 
tures in  the  first  two  preparations  is,  that,  like  the  physic  of  the  homoeo- 
paths, they  do  no  harm  ;  but  I  unhesitatingly  express  a  conviction 
of  an  opposite  nature  regarding  the  last.  I  believe  that  the  constant 
employment  of  the  Turkish  bath  is  calculated  to  increase  the  already 
too  large  per-centage  of  heart  and  kidney  diseases.  My  belief  is 
based  upon  scientific  grounds,  upon  experience  of  the  results  pro- 
duced on  the  health  of  others  by  the  Turkish  bath,  and  upon  the 
circumstance  that  this  abominable  system  of  cooking  human  beings 
is  happily  dying  out. 

When  on  the  subject  of  "  circulation  of  the  blood,"  I  told  you 
that  one  of  the  forces  which  promoted  the  conveyance  of  the  nutri- 
tive fluid  was  that  produced  by  the  muscular  action  of  the  body 
pressing  on  the  veins,  and  that  when  the  blood  was  sent  through  the 
system  with  greater  swiftness  than  usual,  a  part  of  the  work  was 
performed  by  the  muscles.  When  you  are  in  the  Turkish  bath,  your 
blood  is  driven  at  a  fearful  pace  through  your  arteries  and  veins ;  but 
there  is  no  extra  power  developed  by  exertion,  for  you  are  at  rest.  All  the 
labour  falls  upon  the  heart,  which  then  not  only  beats  twice  as  fast  as 
usual,  but  with  more  than  twice  the  force,  for  it  has  to  propel  the  blood 
not  only  through  the  arteries  but  through  the  veins  also.  And  what  is 
the  effect  of  this  ?  The  valves  of  the  heart,  which  are  delicate  folds 
of  membrane,  yield  under  the  undue  pressure,  and  lay  the  foundation 
of  future  endocarditis,  disease  of  the  liver,  and  bowel  complaints, 
horrible  to  contemplate.  But,  my  dear  friend,  this  is  not  all — you 
are  not  benefiting  the  physician  alone,  but  the  surgeon  also.  The 
liquid  secreted  by  the  kidneys  contains  an  amount  of  water  sufficient 
to  dissolve  up  the  salts ;  but  is  this  the  case  when  you  have  been 

*  From  nephroK,  a  kidney,  and  phagein,  to  eat. 

*{•  I  have  been  accustomed  to  designate  this  form  of  medical  treatment 
Pyropathy. 


104  POPULAR  PHYSIOLOGY. 

luxuriating  in  hebdomadal  hot-air  baths  ?  No !  decidedly,  unequi- 
vocally no.  If  I  could  only  reach  your  ear,  and  pronounce  that  negative 
in  an  adequately  impressive  manner,  I  should  be  content.  While  you 
are  ^  sweating  yourself  (like  the  jockey  who  to  diminish  his  weight 
buries  himself  to  the  neck  in  a  dung-hill)  your  kidney  has  been 
secreting  its  ordinary  quantity  of  inorganic  matter— salts ;  but  as 
you  will  have  all  the  water  in  your  skin,  of  course  this  is  not  entirely 
in  a  state  of  solution.  The  undissolved  residue  is  carried  to  the 
bladder,  and  forms  the  nucleus  of  one  of  those  delights  of  middle 
age— calculus,  or  stone  !  Beware,  I  tell  you !  Picture  to  yourself 
that  dreadful  operation-table — ferocious  surgeons,  glorying  in  their 
interesting  case — weapons  compared  to  which  an  Indian's  scalping- 
'knives  are  trifles,  and  that  awful,  awe-inspiring  un-upholstered  and 
undignified  throne — the  lithotomy-stool.  Again  I  say,  be  warned  in 
time  !  That  you  may  see  I  am  sufficiently  impartial  to  consider  both 
sides  of  the  question,  I  give  the  following  series  of  arguments  in 
support  of  the  hot-air  bath : — 

Firstly,— It  has  been  employed  for  centuries  by  the  Turks,  who,  as 
is  well  known,  are  the  most  vigorous  and  energetic  people, 
mentally  and  bodily,  in  the  world— inventors,  philosophers, 
artists,  etc. 

Secondly, — It  was  never  intended  that  man  should  employ  mere 
water  for  the  purpose  of  cleansing  himself— it  being  familiar  to 
comparative  anatomists  that  the  hot-air  bath  has  been  in  use 
among  the  lower  animals  since  their  creation. 

Thirdly, — It  accelerates  the  velocity  of  the  blood,  and  stimulates 
the  heart  to  increased  action,  thus  strengthening  this  organ,  in  the 
same  way  as  excessive  eating  promotes  a  healthy  condition  of  the 
stomach. 

Fourthly, — It  gets  rid  of  all  the  liquid  materials  by  the  action  of 
the  skin,  keeping  the  kidneys  in  reserve  for  old  age,  just  as  by 
constantly  employing  only  one  leg  for  the  purpose  of  locomotion, 
when  it  is  diseased  we  can  make  use  of  the  other. 

Fifthly,— Thousands  of  well-educated  folk  who  believe  in  spirit- 
rapping,  table-turning,  and  Holloway's  ointment,  have  a  profound 
faith  in  the  Turkish  bath  also ;  besides,  it  is  so  pleasant  to  be 
able  to  cure  one's  self  and  shut  the  door  upon  the  doctors. 

To  complete  our  survey  of  the  glands  which  are  to  be  found  in  the 
body  of  man,  I  must  say  one  or  two  words  respecting  three  organs — 
the  spleen  (or  melt,  of  animals),  the  thyroid,  and  the  thymus.  The 
first  is  a  glandular  structure  larger  than  the  kidneys,  and  attached 
to  the  left  end  of  the  stomach.  The  second  rests  against  the  front 
of  the  windpipe,  and  the  last  is  placed  in  the  chest,  behind  the 
breast-bone.  It  is  very  difficult  to  prepare  a  section  of  the  human 
spleen ;  that  of  the  sheep,  however,  admits  of  being  readily  examined 
under  the  microscope,  and  answers  our  purpose  equally  well.  I  regret 
to  say,  our  knowledge  of  the  function  which  this  organ  performs  is 
extremely  vague  and  unsatisfactory,  and  therefore  I  shall  give  in  a 


SPLEEN — THYROID— THYMUS. 


105 


categorical  form  the  opinions  offered  as  to  its  office,  without  entering 
into  further  detail  concerning  it : — 

Firstly, — When  the  blood  cannot  flow  through  the  liver,  it  passes 

backwards  and  dilates  the  spleen,  which  thus  acts  as  a  safety 

valve. 
Secondly,— The  blood-disks  are  renewed  here,  and  waste  matter 

re-manufactured. 
Thirdly,— It  forms  white-of-egg,  from  the  food  which  has  been 

taken  up  by  the  blood-vessels  of  the  stomach,  or  alters  the  blood 

as  it  passes  through. 

Our  acquaintance  with  the  use  of  the  thyroid  and  thymus  glands 
is  quite  as  limited ;  in  point  of  fact,  we  are  utterly  ignorant  of  the 
offices  of  all  three  structures  ;  and  when  learned  lecturers  are  demon- 
strating in  the  most  lucid  manner  the  functions  of  these  mechanisms, 
they  are  not  only  retarding  the  progress  of  science,  but  deceiving 
themselves  and  their  pupils. 

Below  are  representations  of  the  thymus  (fig.  55),  and  thyroid 
organs  (fig.  56) ;  the  latter  as  seen  when  a  delicate  section  has  been 
placed  under  the  microscope. 


Fig.  55. 


.56. 


106 


POPULAE,  PHYSIOLOGY. 


CHAPTER  XII. 

Motion  and  Locomotion — Most  Animals  can  move  from  place  to  place, 
and  some  Plants  have  a  similar  power — The  Limbs — The  three  forms- 
of  Levers — Legs  and  Arms  are  Levers  working  on  pivots  called  Joints 
— Action  of  a  Muscle  upon  a  Limb — Why  bodies  remain  at  rest — 
The  Centre  of  Gravity — We  walk  by  altering  the  position  of  the 
Centre  of  Gravity  and  making  an  effort  to  fall — Structure  of  Muscle — 
Striped  and  unstriped  varieties  of  Muscular  Fibre — How  a  Muscle 
contracts. 

LOCOMOTION  is  a  faculty  possessed  in  its  highest  form  by  animals ; 
although  some  are  denied  the  power,  and  certain  members  of  the 
vegetable  kingdom  enjoy  it.  Many  of  the  lower  animals  are  fixed 
during  life  to  one  spot — their  existence  being  a  stationary  one; 
whilst  some  of  the  most  inferior  plants  are  able  to  move  about  from 
place  to  place  with  great  facility.  In  one  of  the  earlier  chapters  I 
attempted  to  explain  to  you  the  construction  of  the  human  skeleton. 
Here  I  have  to  deal  with  the  limbs  attached  to  it,  in  order  to  show 
you  the  way  in  which  these  are  worked  (in  conveying  the  body  from 
one  locality  to  another,  and  in  carrying  food  to  the  mouth),  by 
the  agency  of  numerous  bands  and  cords  of  flesh,  called  muscles.  Do 
you  know  that  there  are  three  different  kinds  of  levers  ?  First,  that 
in  which  the  pivot,  or  fulcrum,  is  placed  between  the  power  applied 
to  the  lever,  and  the  resistance  or  weight  to  be  overcome.  Of  this  a 
familiar  example  is  the  common  balance,  when  employed  as  delineated 
beneath  (fig.  57) — b  being  the  end  pressed  on,  c  the  pivot,  and  w  the 


Fig.  57. 

weight.  Second,  where  the  pivot  (c)  is  at  one  end,  the  power  (a  k}  at 
the  other,  and  the  weight  (b)  between  the  two — as  at  fig.  58.  And 
third,  where  the  weight  is  at  one  end  (w),  the  power  in  the  middle 
(p),  and  the  pivot  at  the  other  (F,  fig.  59). 

The  limbs,  moving  as  they  do  on  pivots  (joints),  constitute  a  series 
of  levers,  whose  actions  are  often  complex  enough.  Let  us  look  at 
the  arm  (fig.  60).  This  is  a  lever,  whose  fulcrum  is  at  the  shoulder- 
ioint,  and  which  has  another  lever— the  fore-arm  (b,  c,  d)  working 
by  a  hinge  at  its  extremity.  Two  sets  of  muscles  clothe  these 
bones— one  the  flexors,  which  bend  the  fore-arm  on  the  arm,  and  this 


FORMS  OF  LEVERS.  10? 

on  the  chest ;  another,  the  extensors,  which  stretch  out  both,  as 


Fig.  58. 

when  we  point  to  some  distant  object.  The  flexor  muscie  (I  only 
select  one)  of  the  arm  is  attached  above  to  a  fixed  point — the 
shoulder;  and  below  is  conti- 
nuous with  the  bone,  through 
the  medium  of  a  strong,  un- 
yielding, whitish  cord,  the  sinew. 
This  muscle,  when  stimulated 
by  the  nerves,  shortens,  and  in 
this  way  becomes  a  power  ( 0), 
operating  upon  the  lever  (/), 
which  then  is  drawn  inwards, 
carrying  the  weight  (id)  with  it. 
In  the  same  manner  is  the  fore- 


Fig.  59. 


arm  (w)  bent  upon  the  arm,  as  shown  in  the  diagram  (fig.  61) ;' 
both  levers  belonging  to  the  third  class.     By  an  exactly  similar 


Fig.  60. 


Uf- 


108  POPULAR  PHYSIOLOGY. 

set  of  contrivances  on  the  outer  portion  of  the  bones,  is  the 
arm  extended  from  the  body,  and  straightened.  The  head  in  its 
nodding  movements  constitutes  a  lever  of  the  first  kind,  or  is  like  the 
beam  of  a  pair  of  scales.  It  rests  on  two  pivots  (which  practically 
we  may  regard  as  one),  and  muscles  being  attached  to  the  skull 
behind  and  in  front,  according  as  we  cause  the  former  or  the  latter  to 
contract,  we  elevate  or  depress  the  head  respectively. 
In  the  thighs  and  legs  the  same  processes  are  gone  through  in 

moving  these  limbs.  The 
mode  in  which  the  whole 
body  is  carried  forwards, 
as  in  walking,  is  some- 
what complicated.  Why 

^oes  a  c^ia^r  remaul  at 
rest  when  placed  on  its 
four  legs,  and  if  inclined 
to  a  ceitain  extent  why 
does  it  tumble  over? 
Fig.  61.  All  bodies  are  attracted 

by   the  earth ;    but  in 

each  body  there  is  one  particular  point,  which  is  attracted,  as 
it  were,  more  than  all  the  rest,  in  which  the  attraction  culminates  ; 
and  this  is  called  the  centre  of  gravity.  As  long  as  any  solid  body 
intervenes  between  this  centre  and  the  earth,  so  long  will  the  chair, 
or  whatever  it  may  be,  remain  at  rest ;  but  the  instant  it  is  unsus- 
tained,  the  body  naturally  falls.  Thus  (fig.  62) :— Here  (b]  the  centre 

of  gravity,  as  indicated  by 
the  letter  c,  is  placed  above 
the  support  intervening  be- 
tween it  and  the  earth.  If, 
however,  it  be  inclined  till 
the  centre  lies  outside  the 
support,  as  in  the  other  in- 
stance (a],  then  the  body 
falls.  When  a  man  walks, 
he  is  constantly  _  throwing 
his  centre  of  gravity  beyond 

Fi    62_  the  base  of  support,  and  as 

constantly    giving    a   new 

support  to  the  falling  body.  If  you  have  not  forgotten  the  figure  of 
the  leg  and  foot,  you'll  understand  this  at  once.  The  leg  is  attached 
to  the  foot  by  a  sort  of  hinge-joint,  which  permits  it  to  move  upon 
the  latter  backwards  and  forwards.  The  entire  weight  of  the  body 
is  borne  by  the  two  feet ;  and  since  there  are  powerful  muscles  (the 
calf)  uniting  the  heel  and  leg,  it  is  clear  that  when  they  contract— 
the  toes  being  the  fulcrum,  or  pivot,  the  heel  will  be  lifted  from  the 
ground,  carrying  upward,  and  a  little  forward,  the  body.  The  foot, 
then,  is  a  lever  of  the  second  kind— the  fulcrum  being  at  one  end, 
the  elevating  power  at  the  other,  and  the  weight  between  both. 

How  do  we  walk  ?    When  we  stand,  the  plumb-line  from  the  centre 
of  gravity  falls  between  the  feet ;  if  we  wish  to  advance,  we  raise  one 


MOTION  AND  MUSCLE. 


109 


limb  from  the  ground,  and  then,  by  acting  on  the  heel  of  the  other, 
we  throw  the  body  forwards,  elevating  it  a  little  at  the  same  time. 
The  moment  this  is  done,  the  plumb-line  from 
the  centre  of  gravity  will  no  longer  fall  upon 
the  foot,  but  will  lie  over  the  ground  in  front 
of  this  latter,  so  that  the  body  would  instantly 
tumble,  were  it  not  that  the  second  limb  is 
brought  down,  and  thus  the  centre  of  gravity 
being  supported,  so  to  speak,  the  natural  state 
of  things  is  resumed.  By  a  repetition  of  these 
processes  the  individual  continues  to  march 
onward.  Besides  the  upward  and  forward 
movement,  there  is  a  slight  one  from  side  to 
side,  which  is  caused  by  the  body  leaning  a 
little  toward  that  side,  the  leg  of  which  is 
raised-  for,  the  centre  of  gravity  lying  in  a 
plane  between  the  two  feet,  when  one  is  raised 
the  natural  tendency  is  to  bring  the  body  down- 
wards. It  can't  fall  toward  the  supported  side, 
and  therefore  it  does  so,  in  some  measure,  to- 
ward the  unsustained  one.  All  these  different 
motions  combined  give  rise  to  the  oscillation  P.ack>  showing  the  direc- 
which  we  frequently  observe  exhibited  in  Sre  of  gra?fty.  T 

walking.  centre  of  gravity  of  the 

If  we  were  about    to  investigate  into   the  pack  -,  c,  of  the  body ; 
nature  of  the  various  movements  of  the  frame,  C^^f10^^61 
we  should  begin  a  volume  especially — so  nu-  fines   f °om   the 
merous  and  complex  are  their  characters.    We  centres, 
shall  therefore  now  pass  on  to  the  consideration 
of  the    structure  of  muscle,   and  the  mode  in  which  it  shortens 
or  contracts.      Take   the  biceps — a  muscle  which  every  one  has 
heard  of— and  you  will  find  that 
it  is  composed  of  several  smaller 
bundles  of  flesh,  which  in  their 
turn   can  be  decomposed  into 
still  minuter  ones,  and  these  are 
made  up  of  what  are  called  mus- 
cular fibres.     Each    fibre,*    if 
examined  under  the  microscope, 
is  seen  to  consist  of  an  outer 
transparent    structure     resem- 
bling   a    tube,  and    an    inner 
series  of  disks  of  polygonal  form, 
piled  end  to  end,  and  of  which 
there  are  several  rows  arranged 
side  by  side  (fig.  64).  The  disks 
are  separated  from  each  other  by 


Fig.  63. — A  man  and 


three 


.—Striped  Muscular  Fibres. 


*  It  is  not  to  be  supposed  that  I  bind  myself  to  a  belief  in  the  existence 
of  actual  fibres  ;  I  merely  use  the  term  as  being  convenient  for  the  purpose 
of  explanation. 


110 


POPULAR  PHYSIOLOGY. 


a  soft  gelatinous  material,  and  hence,  when  the  so-called  fibre  is 
placed  on  its  side,  the  light  coming  more  strongly  through  one 
part  than  another  produces  an  appearance  such  as  would  be 
observed  if  the  object  were  actually  striated,  on  which  account 
this  form  of  muscle  is  termed  "the  striped  variety"  (fig.  64), 
although  the  striping  is  only  apparent  and  deceptive.  The  muscle 
contracts  by  a  shortening  of  its  constituent  fibres,  which  diminish 
their  length  in  the  following  manner :  Each  disk  widens,  and  ap- 
proaches its  fellows,  at  the  same  time  having  undergone  a  diminution 
as  regards  the  length  of  the  muscle.  By  this  means,  whilst  each 
fibre  shortens,  it  also  thickens  ;  and  this  is  why  a  person  who  is  vain 
of  his  biceps  causes  it  to  contract  before  he  exhibits  it,  knowing  that 
when  in  this  condition  it  is  more  prominent,  from  its  increased  width, 
than  when  in  a  state  of  rest.  The  subjoined  diagrams  (fig.  66  A 
and  B),  delineating  a  row  of  disks  during  contraction  and  relaxa- 
tion, will  assist  you  to  comprehend  the  whole  process : — 


Fig.  65.— Zigzag    condition  of 
muscular  fibres. 


Fig.  66.— Muscular  Fibres.  A,  a  fibrs 
relaxed  j  B,  a  fibre  contracted. 


THE  NERVOUS  SYSTEM. 


Ill 


CHAPTER    XIIL 

The  Nervous  System — Form  and  Structure  of  the  Brain — Cerebrum  and 
Cerebellum  —  Convolutions  —  Medulla  Oblongata  —  Origin  of  the 
Nerves  —  Use  of  the  Brain  —  Experiments  on  Birds  proving  the 
Function  of  the  Cerebrum — White  and  Grey  Nervous  Matter — Brain- 
marks  of  Intelligence  —  Size — Width  —  Number  of  Convolutions  — 
Investigations  of  Wagner — The  Cerebrum  covers  the  Cerebellum,  not 
only  in  Man,  but  in  certain  Apes — Weight  of  the  Human  Brain — 
Function  of  the  Cerebellum — Use  of  the  Spinal  Chord — Description 
of  a  Nerve — How  Nerves  end — Eighteen  Objections  to  the  Doctrines 
of  Phrenologists  —  Comparison  of  the  Skulls  of  various  Nations  — 
Long  Heads  and  Short  Heads  —  Straight  Faces  and  Sloping  Faces — 
The  Ethnologic  Poles — Age  of  Man— Geological  Evidence  to  prove  the 
Immense  Period  that  has  elapsed  since  Man's  First  Appearance. 

COMPLEX  and  difficult  t9  be  understood  as  the  various  organs  we 
have  hitherto  been  considering  may  have  seemed,  those  which  we 
are  about  to  begin  the  study  of  are  the  greatest  puzzle  of  all ;  and, 
indeed,  were  it  not  that  one  could  hardly  omit  their  consideration,  I 
should  gladly  have  left  ., 

them  out,  for  I  conceive,          *  *  «jrf<  .f  .ff.Jf,J  K 

that  even  though  1  bring 
forward  the  most  advanced 
views  upon  the  subject,  I 
shall  still  be  but  propaga- 
ting error ;  the  physiology 
of  the  Nervous  System,  and 
the  nature  of  life  itself 
being  so  firmly  united,  that 
it  is  (if  possible)  extremely 
difficult  to  thoroughly  un- 
derstand the  former  with- 
out a  clear  conception  of 
the  latter.  And  since  we 
do  not  possess  this^  it 
appears  to  me  to  be  wiser 
to  store  up  our  facts  till 
such  time  as  we  can  explain 
them  thoroughly,  than  put 
them  before  the  public 
dressed  and  varnished,  ac- 
cording to  the  fashion  of 
pseudo-fScience. 

You  will  kindly  accept 
the  above   remarks  as  an 


apology   for   the    general  the  filaments. 


Fig.  67.— Ultimate  Xerve  Filaments,  as  seen 
under  the  microscope.  The  fibres  of  the  two 
sets  are  seen  to  cross  and  intermingle,  without 
however  losing  their  distinctness.  The  capitals 
indicate  the  sheathes  of  the  nerve*,  the  italics 


112 


POPULAll  PHYSIOLOGY. 


Nerve  ^ 
of  I 
face.  J 
Networ  S 
of  arm-  > 
nerves.  ) 


Nerve      -> 
of 

skin.       ) 


Nerve  of  ) 
thumb,  j 
Nerve  of  S 

little     I 
finger.   J 


Network^ 
of  thigh  [ 
nerves.  ) 


Nerves 
of  legs. 


_»  Brain. 

—  Lesser  brain. 

—  Spinal  chord. 


[ribs. 
' —    Nerves  of 

\ (  Network 

J.  of  hip 
(.nerves. 


(  Nerves 

(  of  legs. 


Fig. 


STRUCTURE  OF  NERVE-TISSUE. 


113 


mode  of  treatment    of  the  nervous  system  which  I  shall  adopt  in 
the  following  pages. 

A  glance  at  the  diagram  will  convey  to  you  a  notion  of  the  extent 
and  character  of  the  entire  nervous  apparatus. 

It  consists  of  a  central  chord  of  a  whitish-grey  colour,  enclosed  in  the 
channel  formed  by  the  arches  of  the  vertebrae  (back-bone),  expanding 
above  into  the  brain,  and  giving  out  from  its  sides  numerous  branches — 
nerves— which  pass  to  the  limbs  and  various  regions  of  the  body.  If 
we  were  to  place  a  particle  of  nervous  matter  beneath  the  microscope 
we  should  perceive  that  it  was 
composed  of  two  very  different 
structures— a  number  of  more 
or  less  egg  -  shaped  vesicles, 
and  a  series  of  fibres  or  fila- 
ments (fig.  73,  A  and  B).  It 
is  thought  that  the  nervous 
power,  whatever  it  may  be 
(that  which  stimulates  the 
muscles  to  contraction, — the 
glands  to  secretion, — the  mind 
to  the  formation  of  ideas), 
resides  in,  and  is  developed 
by  the  vesicles  ;*  whilst  the 
office  of  the  fibres  is  to  convey 
this  power  from  the  vesicles 
to  the  muscle  or  gland,  or  to 
convey  an  impression  from  the 
surface  of  the  body  to  the 
vesicular  substance.  The  brain 
and  great  chord,  or  spinal 
chord,  as  it  is  more  frequently 
termed,  are  composed  super- 
ficially of  this  vesicular  mate- 
rial, and  hence  it  is  supposed 
that  in  these  two  organs  lie 
the  peculiar  powers  of  nervous 
tissue.  If  we  were  to  examine 
the  brain  minutely,  it  would 
form  a  pursuit  for,  I  might 
almost  say,  a  life-time,  and  in  the  end  we  should  find  much  of 
bur  study  flat  and  unprofitable ;  for  of  what  interest  could  the 
arrangement  of  its  component  parts  be  to  one  who  was  entirely 
ignorant  of  their  purposes  ? 

When  we  look  down  upon  the  human  brain  (fig.  70)  we  see  a  whitish- 
grey,  waxy-looking  mass,  of  an  oval  outline,  whose  surface  is  curiously 
grooved  and  elevated,  presenting  many  eminences  and  depressions, 
which  at  first  sight  appear  to  constitute  a  kind  of  labyrinth— these 
are  the  convolutions,  so  often  alluded  to  by  those  itinerant  charlatans, 


Fig.  69.— Cluster  (technically,  a  ganglion) 
of  nerve  vesicles,  with  nerve-filaments 
passing  through  it. 


*  This  view  is  at  least  questionable. 
I 


14  POPULAR  PHYSIOLOGY. 

phrenological  lecturers.  This  upper  structure  is  the  true  brain,  or 
cerebrum ;  it  is  divided  by  a  central  groove,  passing  from  front  to 
back,  into  two  portions  or  hemispheres,  and 
each  of  these  by  cross  divisions  into  three 
smaller  ones,  called  lobes— a  front,  middle, 
and  back.*  On  raising  the  cerebrum  behind 
we  observe,  what  till  then  were  hidden  two 
small  hemispheres,  united  in  the  centre, 
and  which  are  collectively  _  styled  the  cere- 
bellum, or  lesser  brain.  This  organ  presents 
no  true  convolutions ;  it  is  attached  on  the 
one  hand  to  the  cerebrum,  and  on  the  other 
to  the  spinal  chord,  the  upper  part  of  which 
is  contained  within  the  skull.  The  cerebrum, 
or  true  brain,  constitutes  about  six-sevenths 
of  the  entire  amount  of  nerve-substance 
70t  contained  in  the  cranium  (skull),  the  remain- 

ing seventh  being  represented  by  the  cere- 
bellum. The  latter,  in  man,  is  completely  concealed  by  the  cerebrum, 
and  when  in  its  natural  position  is  separated  from  it  by  a  peculiar 
tent-like  membrane,  which  is  stretched  across  like  an  arch  from 
one  side  of  the  skull  to  the  other,  in  the  back  part  of  the  cavity ; 
upon  this  the  posterior  lobes  of  the  cerebrum  rest,  and  beneath  it 
lies  the  cerebellum. 

To  that  part  of  the  chord,  or  marrow,  which  lies  within  the  brain-case, 
is  given  the  name  of  "  medulla  oblongata,"  and  this,  as  I  mentioned 
before,  is  continuous  with  the  brain,  through  the  cerebellum.  The 
entire  cerebro-spinal  system  (brain  and  spinal  marrow)  is  enclosed  in 
three  membranes,  which  lie  one  within  the  other;  the  outer  being  the 
strongest  and  least  vascular,  the  inner  the  most  delicate  and  abun- 
dantly supplied  with  blood-vessels.  This  latter  covering  sinks  into 
the  various  fissures  and  divisions  of  the  brain,  and  in  fact  has  much 
to  do  with  the  nutrition  of  that  organ.  The  brain  is  not  solid 
throughout,  as  we  may  see  by  slicing  away  its  substance  horizontally,^ 
when  we  come  upon  two  very  large,  irregularly  shaped  cavities,  of 
the  same  form,  termed  the  lateral  ventricles-  and  by  making  other 
sections  we  come  across  other  cavities  also.  IN  either  is  it  a  shapeless 
mass  internally,  for  within  the  cavities  we  detect  certain  prominences 
and  depressions,  to  which  very  pedantic  names  are  given,  but  whose 
functions,  I  may  safely  say,  we  know  nothing  of. 

If  we  turn  to  the  base,  or  under  portion  of  the  brain,  we  observe 
that,  like  the  upper,  it  has  upon  its  surface  many  convolutions,  which  fit 
into  corresponding  pits  or  hollows  in  the  bone.  Besides,  we  see, 
towards  its  front  extremity,  two  soft,  thin,  somewhat  club-shaped 
appendages ;  these  are  the  "  olfactory  lobes,"  or  nervous  masses  which 
preside  over  the  sense  of  smell.  Resting  upon  the  bones  above  the 

*  Neither  the  median  groove  nor  the  cross  ones  extend  deeply  enough  to 
separate  the  lobes  from  each  other  completely ;  there  still  remains-  a 
quantity  of  nervous  matter,  by  which  they  are  united  beneath. 


CHARACTERS  OF  THE  BRAIX.  115 

nostrils,  they  send  down  through  the  several  minute  apertures,  small 
filaments  to  the  delicate  membrane  of  the  nose.  Looking  more  towards 
the  middle,  we  remark,  placed  between  the  two  median  lobes,  the 
optic  nerves  passing  from  without  inwards,  and  uniting  with  each 
other  prior  to  their  final  separation  on  their  journey  to  the  eyes. 
Next  glancing  backwards,  we  perceive  an  arched  prominence ;  this  is 
styled  the  pons  or  bridge  of  Varolius,*  and  is  composed  of  a  series 
of  fibres  travelling  from  one  side  of  the  cerebellum  to  the  other,  and 
beneath  which  flows  a  stream  of  nervous  filaments  from  the  cerebrum, 

|  Uniting 

Front  lobe.  band.      Middle  lobe.  Hind  lobe. 


Spinal  Chord. 
Fig.  71. 

which  enter  the  medulia  oblongata.  This  organ  is  but  the  extremity 
of  the  spinal  chord ;  its  most  important  character  is,  that  within 
it  the  rows  of  nervous  cells  connected  with  the  nerves  of  the  muscles 
cross  each  other,  those  of  the  right  side  of  the  chord  passing  to 
the  left  side  of  the  brain,  and  those  of  the  left  side  of  the  chord  to 
the  right  side  of  the  brain,  f 

The  spinal  marrow  itself  is  divided  by  longitudinal  fissures  (one 
behind,  the  other  in  front)  into  two  lateral  columns,  which  together 

*  A  distinguished  anatomist  of  Bologna,  died  1578. 
f  This  is  the  reason  why,  when  the  left  hemisphere  of  the  cerebrum  is 
injured,  the  right  side  of  the  body  is  paralyzed. 

i2 


116 


POPULAR  PHYSIOLOGY. 


form  a  more  or  less  flattened  cylinder.  A  transverse  section  shows 
that,  though  it  is  white  externally,  it  contains  a  considerable  quantity 
of  grey  matter  in  its  interior;  this  is 
arranged  in  the  form  of  two  crescents, 
one  in  each  lateral  half ;  they  have  their 
convex  borders  within,  and  hence,  facing 
each  other— a  transverse  band  of  grey 
substance  forming  a  band  of  union  be- 
tween the  two  ;  their  concave  edges  look 
outwards,  the  horns  projecting  almost  to 
the  surface  of  the  chord. 

We  see,  springing  from  the  chord, 
along  its  entire  length  from  the  skull  to 
the  hips,  no  less  than  sixty-two  nerves, 
thirty-one  on  each  side;  these  travel 
between  the  vertebra  to  the  various 
muscles  of  the  body,  and  also  to  the 
general  surface  or  skin,  sending  out  nu- 
merous branches  as  they  journey  to  their 
different  destinations.  If  we  look  at 
one  of  these  nerves,  and  observe  how  it 
is  connected  to  the  chord,  we  shall  ob- 
serve that  it  does  not  become  attached 
as  a  single  string,  but  that  it  splits  dis- 
tinctly into  two  portions,  one  of  which 
enters  the  back  part,  and  is  almost 
continuous  with  the  hind  horn  of  the 
grey  crescents,  the  other  entering  in 
front,  and  having  some  connection  with 
the  front  horn ;  now  these  two  origins 
of  each  nerve  are  designated  the  anterior 
and  posterior  roots  respectively. 

There  is  another  portion  of  the  ner- 
vous apparatus,  the  study  of  which  has, 
till  within  the  last  few  years,  received 
very  little  attention.  This  is  tne  sympa- 
thetic system,  as  it  has  been  called,  from 
the  supposition  that  it  exerts  a  specially 
sympathising  influence  over  the  dif- 
ferent organs.  The  sympathetic  system 
is  composed  of  a  number  of  clusters  of 
nerve-cells  (ganglia^),  which  are  situate  in 
the  neck  and  trunk,  on  each  side  of  the 
back-bone.  These  clusters  are  connected 
by  filaments,  and  thus  the  entire  series 
constitutes  a  perfect  whole.  These  ner- 
vous chains  are  directly  connected  with 
the  spinal  marrow,  and  have  numerous 
communications  with  the  ordinary 
nerves ;  they  supply  branches  to  the  glands,  and  to  several  other 


Fig.  72.— Brain  and  Chord 
seen  from  the  front,  a,  the 
cerebrum;  b,  the  front  lobe; 
c,  middle  lobe ;  d,  hind  lobe ; 
e,  the  cerebellum ;  /,  the  me- 
dulla oblongata ;  g,  the  nerves 
of  the  neck  ;  h,  nerves  of  hips ; 
»,  end  of  spinal  chord;  k,  great 
nerve  of  thigh. 


FUNCTION  OF  THE   CEREBRUM. 


117 


organs,  but  their  exact  distribution  is  not  yet  understood.  It  has 
somewhat  recently  been  shown,  that  the  minute  blood-vessels  (capil- 
laries) are  all  supplied  with  filaments  from  this  system ;  but  of  this 
more  afterwards. 

It  seems  almost  an  idle  question  to  ask,  What  is  the  exact  use  of 
the  brain  proper  ?  and  I  should  not  be  at  all  surprised  to  hear  one 
exclaim,  "  Everybody  knows  that  it  is  the  seat  of  the  mind !  "  Every- 
body does  not  know  that  it  is  the  organ  of  thought;  everyone 
has  heard  so,  and,  like  many  of  our  so-called  beliefs,  it  is  the  off- 
spring of  education.  However,  both  experiment  and  disease  show 
us  that  it  is  the  seat  of  the  mind,— of  the  intelligence,  of  feeling, 
thought,  and  will.  When  the  cerebrum  of  a  pigeon  has  been  sliced 
away  piece  by  piece,*  the  animal  loses  all  consciousness,  falls  into  a 
state  of  the  most  intense  slumber,  and  is  with  difficulty  roused  by  the 
application  of  external  stimuli ;  nevertheless,  the  ordinary  processes 
of  the  body, —  respiration,  circulation,  secretion,  and  digestion,—  go 
on  as  usual ;  but  thought  and  volition  are  lost.  Thus,  if  food  be  placed 
it  its  mouth,  it  will  be  swallowed  and  digested,  but  the  bird  will  never 
go  in  search  of  it ;  if  a  pistol 
be  fired  close  to  the  head,  the 
sensation  produced  by  the 
sound  will  be  developed,  but 
the  organ  of  thought  being 
absent,  the  report  of  the 
weapon  will  not  be  associated 
with  any  idea  of  alarm,  and 
the  animal  will  remain  in  the 
same  situation  as  before.  If 
the  membranes  covering  the 
cerebrum  be  injured  by  disease, 
as  in  inflammation,  delirium 
supervenes.  If  the  brain  itself 
be  diseased,  some  of  the 
mental  faculties  are  impaired.  Fig.  73. 

If  the  skull,  and,  consequently, 

the  cerebrum,  be  injured  fjy  fracture,  serious  mental  derangement 
follows.  All  these  facts  point  to  one  and  the  same  conclusion,  viz., 
that  in  the  cerebrum  are  located  the  various  faculties  of  the  mind. 

The  cerebrum  is  composed  of  two  distinct  structures,  an  internal 
mass  of  fibres  (?)  whicn  are  white,  and  an  external  stratum  of  cells 
which  are  grey.  It  is  supposed  that  the  latter  are  connected  with 
the  intellectual  powers,  and  that  the  former  are  merely  the  conductors 
of  impressions  from  without,  and  of  voluntary  impulses  from  withm.f 
I  do  not  think  that  this  has  been  proved  to  be  the  function  of  the 
central  mass  of  the  cerebrum ;  but,  be  that  as  it  may,  the  idea  that 

*  The  bird  suffers  no  pain  when  the  cerebrum  is  being  removed,  for  this 
organ  is  quite  insensible  to  torture.  The  brain  of  man  has  occasionally 
been  incised  without  the  production  of  the  slightest  painful  sensation. 

t  From  the  body  to  the  brain,  and  vice  versa. 


118  POPULAR  PHYSIOLOGY. 

the  grey  matter  is  connected  (in  its  entirety)  with  the  mental  opera- 
tions, is  supported  by  the  following  facts : — 

First.  In  infancy,  and  during  foetal  life,  when  the  intelligence  is 

either  at  its  minimum,  or  nil,  the  quantity  of  grey  substance  is 

very  small. 
Second.  In  idiots  there  is  a  proportionally  smaller  quantity  than  in 

intelligent  men. 
Third.  As  we  pass  in  the  scale  of  beings  from  fishes  to  man,  we 

find  the  quantity  of  grey  matter  increasing. 

If  the  cerebrum  of  man  were  simply  a  convex  mass,  with  a  smooth 
surface,  it  is  obvious,  that  as  the  grey  matter  formed  only  an  external 
coat,  the  entire  amount  could  not  be  very  great ;  but  it  being  neces- 
sary for  the  offices  of  the  mind  that  a  larger  surface  should  be  present, 
we  find  that  in  the  human  cerebrum  there  is  a  peculiar  arrangement 
by  which  the  superficial  area  is  vastly  increased.  This  consists  in  the 
existence  of  numerous  deep  grooves,  which  traverse  the  surface  in 
every  direction,  and  whose  sides  and  bottoms  are  lined  with  grey 
matter.  If  you  cannot  understand  how,  by  this  means,  the  extent  of 
surface  is  magnified,  fancy  that  the  grey  material  is  a  napkin,  with 
which  it  is  required  to  cover  the  brain.  If,  now,  it  be  only  required  to  lay 
the  cloth  over  the  surface,  a  very  small  towel  will  suffice ;  if,  however, 
it  be  necessary  to  allow  the  cloth  to  dip  into  an  immense  number  of 
grooves,  a  very  large  towel  must  be  employed. 

p  We  find  that,  to  a  certain  extent,  the  amount  of  intelligence  is  in 
direct  proportion  to  the  quantity  of  the  grey  substance,  and  that, 
therefore,  the  animals  whose  brains  are  grooved  (convoluted)  are  the 
more  intelligent.  This  holds  good  only  within  certain  limits ;  for 
example,  an  animal  may  have  numerous  convolutions,  and  yet,  from 
the  fact  that  the  grooves  are  of  no  great  depth,  the  amount  of  surface 
is  smaller  than  we  might  have  at  first  supposed,  and  hence  the  exhi- 
bition of  intelligence  is  also  minus. 

It  is  no  easy  matter  to  erect  any  cerebral  standard  of  intelligence, 
when  we  come  to  contrast  the  brain  of  the  apes  with  that  of  the 
human  subject.  Many  writers,  however,  assert  that  the  following 
features  are  indicative  of  the  possession  of  great  intellectual  powers : 
large  absolute  size ;  width ;  number  of  convolutions  ;  the  fact  that 
the  cerebrum  completely  covers  in  the  cerebellum,  so  that  when 
the  brain  is  looked  down  on  from  above,  no  portion  of  the  cerebellum 
can  be  detected;  great  weight. 

We  shall  consider  each  of  these  marks  (?)  of  intelligence  seriatim, 
and  we  shall  see  that  they  are  at  the  best  fallacious. 

ABSOLUTE  SIZE  :— When  the  brain  is  exceedingly  small,  we  not 
unfrequently  find  that  the  former  proprietor  was  an  idiot ;  but  con- 
versely, we  do  not  always  find  idiots  with  brains  below  the  average 
size,  and  very  often  it  happens  that,  of  two  fools,  he  with  the  bigger 
head  is  the  greater.  Phrenologists  talk  a  good  deal  of  the  great  size  of 
the  brain  of  Cuvier ;  but  they  make  no  mention  of  the  small  size  of 
Sir  Walter  Scott's,  nor  of  that  of  Locke's,  whose  mental  powers 
were  possibly  quite  as  extensive  as  those  of  the  great  anatomist. 


BRAIN-STANDARD  OF  INTELLIGENCE.  119 

Moreover,  man  does  not  possess  the  largest  brain  absolutely ;  that  of 
the  elephant,  and  also  of  the  whale,  being  individually  greater  and 
more  bulky.  Neither  is  it  relatively  the  largest,  that  of  the  common 
sparrow  being  more  voluminous  in  proportion  to  the  size  of  the  body. 
Again,  if  size  were  to  be  taken  as  a  standard  of  intelligence,  the 
degraded  Negro  should  be  regarded  as  possessed  of  as  much  intel- 
lectual power  as  the  European ;  for  the  researches  of  the  most  dis- 
tinguished Dutch  anatomists  have  shown  that  the  negro  brain  is 
quite  as  large  as  that  of  the  Caucasian  and  other  races. 

WIDTH :  It  is  a  popular  conception  that  a  man  with  a  large  forehead 
must  needs  be  a  man  of  great  mental  power ;  but  this  does  not  follow 
as  a  logical  consequence.  Indeed,  we  find  the  widest  skulls  among 
the  inhabitants  of  the  north-east  of  Asia  j  but  I  am  not  aware  that 
the  people  of  those  regions  are  characterised  by  a  more  than  usual 
possession  of  intelligence. 

NUMBER  OF  CONVOLUTIONS  :  This  affords  no  true  key  to 
the  mental  character  of  the  individual.  Many  of  the  lower  animals  have 
(according  to  good  authorities)  quite  as  many  convolutions  as  man, 
and  yet  hold  a  very  inferior  position  in  the  intellectual  scale ;  and 
certain  birds,  which  have  no  convolutions  at  all,  are  vastly  more  saga- 
cious than  quadrupeds  whose  brains  are  ploughed  by  numerous 
furrows.  It  has  been  stated  also,  by  a  most  illustrious  anatomist,  who 
paid  much  attention  to  this  subject,  that  "the  brains  of  some  very 
intelligent  men  were  among  those  poor  in  convolutions."  * 

With  reference  to  the  position  of  the  cerebellum,  as  indicative  of 
the  presence  or  absence  of  intelligence,  but  little  can  be  said  with 
accuracy.  One  distinguished  anatomist  holds,  that  in  man  alone  is 
the  cerebellum  completely  covered  in  by  the  cerebrum,  and  he  there- 
fore looks  upon  the  position  of  the  former  in  the  human  brain  as 
indicating  the  presence  of  high  mental  powers;  however,  many  inves- 
tigations into  the  position  of  the  lesser  brain  in  apes  have  been  made 
within  the  last  three  years,  and  unfortunately  for  the  superior  cerebral 
character  of  man's  brain,  it  has  been  demonstrated  that  the  cerebellum 
in  some  of  the  former  animals  is  also  concealed  by  the  cerebrum,  and 
that  the  difference  between  the  extent  of  cerebellum  covered,  in  man 
and  in  the  ape,  does  not  amount  to  the  one-tenth  of  an  inch. 

THE  WEIGHT  of  the  brain  of  an  adult  male  European  varies  be- 
tween 3  Ib.  2  oz.  and  4  Ib.  6  oz. ;  that  of  a  female  varies  between  2  Ib.  8  oz. 
and  3  Ib.  11  oz.  The  lesser  weight  of  woman's  brain  does  not  show  any 
mental  inferiority;  for  it  must  be  borne  in  mind  that  the  average  female 
body  is  much  smaller  than  the  average  male  one,  and  that,  therefore, 
her  brain  organs  are  present  in  due  proportion.  If  her  brain  were  as 
large  as  man's,  then  by  the  same  line  of  reasoning  she  should  be  the 
superior  being,  for  her  cerebral  system  relatively  to  her  trunk  would 
be  much  greater  than  that  of  man.  Those  who  assert  that  absolute 
weight  of  brain  is  a  standard  of  mental  force,  should  recollect  that 
although  it  is  known  that  the  brains  of  Cuvier,  Cromwell,  and 
Dupuytren,  far  exceeded  the  average,  yet  we  have  little  evidence  as 

*  Wagner,  in  the  "  Gottingen  Nachrichten"  for  1860,  No.  7. 


120  POPULAR  PHYSIOLOGY. 

to  whether  very  intelligent  men  may  not  have  light  brains,  and  that 
ere  they  give  their  support  to  a  theory  they  should  have  evidence  on 
both  sides.  Wagner  asserts  most  positively  that,  the  brains  of  intelli- 
gent persons  cannot  be  proved  to  be  heavier  than  those  of  individuals  less 
gifted  in  mental  attributes.  For  my  own  part,  I  must  confess  that  it 
seems  to  me  unfair  to  draw  any  conclusions  from  the  existence  of 
slight  distinctions  as  to  weight,  because  it  is  impossible  by  this  means 
to  form  an  exact  estimate  of  the  quantity  of  nervous  matter  present, 
inasmuch  as  no  precise  deduction  can  be  made  for  the  blopd  or  serous 
fluid  which  may  be  present.  Thus,  one  man  may  die  while  his  brain 
has  been  much  excited,  and,  although  he  may  have  been  devoid  of  any 
great  mental  powers,  his  brain,  owing  to  its  being  charged  with  blood, 
will  weigh  more  than  it  would  were  the  mere  nervous  matter  con- 
sidered. Again,  a  man  who  has  been  distinguished  for  his  talents, 
thought,  and  so  forth,  may  die,  and  from  the  fact  that  previous  to  his 
death  his  mind  had  been  very  slightly  excited,  his  brain  will  weigh  far 
less  than  we  should  have  supposed. 

From  the  above  remarks,  the  reader  may  conclude  that  we  cannot 
place  much  reliance  upon  any  one  of  the  characters  I  have  mentioned, 
if  we  wish  to  be  guided  accurately  to  a  fair  decision.  There  are, 
however,  two  important  features  in  the  brain  of  the  European  which 
at  once  distinguish  him  from  the  lower  animals.  First,  his  brain  is 
larger  in  proportion  to  the  nerves  which  emanate  from  it  than  that  of 
any  other  animal;  and  second  (a  character  which  has  of  late  been  much 
dwelt  on),  his  brain  is  vertically  vastly  higher  than  that  of  any  existing 
being.  This  character  of  altitude  seems  to  form  the  great  line  of 
demarcation  between  man  and  his  fellow  animals,  and  is  I  believe 
the  only  one  upon  which  we  can  place  dependence.  A  great  many 
people  of  a  would-be  religious  turn  of  mind  have  been  greatly  horri- 
fied during  the  last  couple  of  years  by  the  notion,  that  "  man  and  the 
monkey  "  are  in  physical  features  so  closely  allied.  Why  they  should 
have  been  so  seized  seems  to  me  inexplicable.  I  conceive  that  the 
anatomical  characters  of  man's  brain  do  not  explain  why  he  possesses 
so  much  intelligence.  Let  us  suppose  that  mind  is  entirely  the 
offshoot  of  brain,  then  the  brain  of  man  has  a  certain  intellectual 
value ;  now  the  brain  of  the  ape  must  similarly  have  a  constant  intel- 
lectual value  ;  and  since  the  distinction  between  the  brains  of  the  two 
animals  (anatomically)  is  perceived  with  difficulty,  so  is  the  intellectual 
difference  hardly  perceptible,  a  conclusion  which  (I  need  not  say)  is 
absurd.  I  think  then  that  the  charge  of  materialism  which  has 
been  urged  against  those  who  elevated  the  ape  anatomically,  is  far 
more  justly  applicable  to  those  pseudo -philosophic  conservatives  who 
would  force  on  themselves  the  faith  in  man's  immense  cerebral  superi- 
ority. From  all  that  we  have  seen,  then,  we  may  pretty  safely  say 
that  the  cerebrum  is  the  seat  of  the  mind,  and  that  in  man  it  differs  to 
some  extent  from  that  of  the  ape,  but  certainly  not  in  proportion  to  the 
highly  developed  mental  qualities  of  the  former. 

What  is  the  function  of  the  cerebellum  is  the  next  question  to 
which  we  shall  apply  ourselves.  As  to  its  office,  there  are  two  views 
current, — an  old  and  a  recent  one.  The  first  holds  that  it  is  the  organ 


WHAT  IS  THE  USE  OF  THE   CEREBELLUM?  121 

of  amativeness,  and  has  been  especially  espoused  by  phrenologists. 
Scientific  men  of  the  present  day  put  no  credence  in  this  doctrine,  for 
the  following  reasons  : — 

First.  When  it  has  been  removed  artificially,  or  has  been  congeni- 
tally  absent,  the  amatory  passions  have  been  as  intense  as  usual. 

Secpnd.  In  animals  which  have  been  emasculated,  it  is  larger  than 
in  those  which  are  in  their  natural  condition. 

Third.  It  is  large  in  animals  whose  passions  are  slight,  and  feebly 
developed  in  those  whose  feelings  are  very  intense. 

The  second  opinion  as  to  its  function  is  more  rational.  It  is 
thought  that  the  cerebellum  presides  over  muscular  actions,  enabling 
a  series  of  movements  to  be  combined  in  such  a  manner  that  a  certain 
end  is  attained— as,  for  example,  in  walking,  leaping,  dancing,  &c. 

A  pigeon  whose  cerebellum  had  been  removed,  though  in  the  pos- 
session of  all  its  senses,  and  of  volition  and  thought,  could  not  move 
its  limbs  in  order  (so  to  speak).  It  was  to  all  appearance  intoxicated — 
would  move  one  limb  first,  and  quite  independently  of  the  other ;  and 
similarly  with  its  wings,  so  that  it  stumbled  about  without  advancing. 
This  was,  of  course,  an  experiment,  produced  by  artificial  means ;  but 
disease  also  supplies  us  with  experiments,  which  are  often  more, 
valuable  than  those  conducted  within  our  laboratories.  When  the 
cerebellum  is  diseased  the  same  want  of  co-ordinating  power  is  ob- 
served that  was  exhibited  by  the  pigeon.  A  man  afflicted  in  this 
manner  can  make  no  complex  movements,  and  occasionally  is  seen  to 
spin  violently  round  and  round  in  one  direction,  or  to  roll  over  and 
over  upon  the  ground.  In  what  particular  manner  the  cerebellum 
performs  its  work  we  cannot  tell ;  it  is  one  of  those  mysteries  of  the 
nervous  system  which  it  will  require  the  labour  of  centuries  to  un- 
ravel ;  all  we  can  say  is  this  :  it  holds  the  same  relation  to  the  dif- 
ferent muscles  of  the  body  that  the  conductor  of  an  orchestra  does  to 
the  musicians.  In  both  cases,  were  there  nothing  to  regulate,  as  it 
were,  the  time,  each  of  the  many  units  9f  the  entire  combination  would 
act  irrespectively  of  the  others,  and  instead  of  a  harmonious  result 
we  should  have  but  discord  and  confusion.* 

The  oblong  marrow,  or  medulla  oblongata,  as  it  is  more  technically 
styled,  has  two  uses :  it  conveys  the  cell-rows  of  the  spinal  cord  to 
the  cerebrum  and  cerebellum,  and  is  said  to  preside  over  the  function 
of  respiration ;  for,  when  it  has  been  punctured  or  destroyed,  com- 
plete asphyxia  or  suffocation  ensues.  From  it  spring  the  important 
nerves  which  supply  the  lungs,  larynx,  and  stomach ;  and  it  contains 
within  it  a  small  centre  of  grey  matter,  which  is  named  the  "  vital 
spot,"  because  when  even  touched,  life  ceases.  This  fact,  when  we 
have  given  the  subject  no  consideration,  appears  extraordinary  ;  but 
when  we  know  that  nerves  supplying  tne  larynx,  lungs,  heart, 

*  It  must  be  here  stated  that  even  this  view  of  the  function  of  the 
cerebellum  is  open  to  the  very  serious  objection,  that  in  some  cases  of 
cerebellar  disease  the  muscular  movements  are  unimpaired. 


122  POPULAR  PHYSIOLOGY. 

stomach,  and  liver  all  take  their  rise  in  the  vicinity  of  this  particular 
region,  much  of  our  surprise  is  lost. 

The  spinal  chord  has  a  two-fold  office.  First,  it  serves  to  convey  to 
the  brain  various  impressions  which  have  been  received  at  the  surface 
of  the  body  (skin,  fingers,  etc.),  and  carried  to  it  by  the  nerves  of 
sensation ;  and  also  to  convey  from  the  brain  the  impulse  of  the  will 
to  those  nerves,  which,  passing  from  the  chord,  are  distributed  among 
the  muscles.  Second,  it  operates  as  a  sort  of  animal  brain,  possessing, 
as  it  were,  a  kind  of  consciousness,  which  enables  it  to  superintend 
the  working  of  such  organs  as  the  gullet,  without  the  interference  pf 
the  true  brain.  Thus,  when  we  sleep,  it  is  requisite  that  certain 
actions  be  performed— as,  for  example,  the  contractions  of  the  dia- 
phragm, the  elevation  of  the  ribs,  &c.,  &c. ;  and  if  these  offices  were 
placed  under  the  direction  of  the  will,  it  is  evident  that  on  falling 
asleep  we  should  forget  them,  and  that  we  should  therefore  be  suffo- 
cated. Now  the  spinal  chord  (being,  in  a  manner,  a  brain),  being 
aware  of  the  necessity  for  the  performance  of  these  functions,  stimu- 
lates the  organs,  and  these  discharge  their  duties,  even  though  the 
chord  be  completely  severed  from  the  true  brain.  To  this  process, 
in  its  entirety,  the  term  reflex  action  has  been  given,  to  distinguish  it 
from  the  ordinary  operations  of  the  animal,  which  are  the  result  of 
volition.  As  we  shall  now  see,  the  term  is  likely  to  lead  us  astray. 
How  is  this  reflex  or  reflected  action  produced?  The  lungs  (if 
respiration  be  interrupted)  become  charged  with  venous  blood,  and 
produce  a  peculiar  impression,  which  is  transmitted  to  the  upper  p^  art 
of  the  chord  (or  possibly  directly),  and  from  it  to  the  middle  portion, 
which  then,  by  influencing  the  nerves  proceeding  to  the  muscles, 
causes  them  to  contract,  and  in  this  way  recommence  the  respiratory 
process,  which  had  been  interrupted.  In  this  case  some  suppose  that 
the  nervous  influence  transmitted  to  the  chord  was  reflected  from  it 
to  the  muscles  ;  but  this  is  purely  a  supposition — the  process  bearing, 
on  the  whole,  a  great  resemblance  to  our  ordinary  voluntary  acts  • 
these  being  invariably  the  result  of  either  an  impression  generated 
in  the  mind,  or  conveyed  to  the  nervous  centre  from  without,  and 
might  with  some  show  of  reason  be  called  reflex.  In  neither  case  is 
the  nerve  force  reflected,  but  in  both  the  centre  is  stimulated,  by  some 
impression,  to  develope  force,  which  is  then  borne  along  the  motor 
nerve  to  the  muscle. 

I  mentioned  before  that  the  nerves  enter  the  chord  by  two  roots  : 
a  front  and  back.  Now,  these  roots  have  very  distinct  properties— 
the  front  being  connected  with  motion,  and  the  back  with  sensation ; 
therefore,  as  these  combine  to  form  a  single  nerve,  it  is  evident  that 
each  nerve  is  compound — that  is  to  say,  it  contains  some  fibres  whose 
office  it  is  to  convey  impressions  to  the  chord,  and  others  which  serve 
to  carry  a  motor  impulse  from  the  chord  to  the  muscles. 

A  description  of  one  nerve  will  suffice  for  all.  It  leaves  the  verte- 
bral column  as  a  single  whitish  chord,  but  as  it  travels  towards  the 
surface  of  the  body,  it  divides  and  subdivides,  sending  off  numerous 
branches  to  the  different  muscles  and  such  like,  and  eventually  ter- 
minates in  the  skin.  The  quantity  of  ultimate  nerve  fibres  contained 


DISTRIBUTION  AND  TERMINATION  OF  NERVES. 


123 


I 


in  any  nerve  is  almost  immeasureable  (a  single  fibre  rarely  ex- 
ceeding one  four-thousandth  of  an  inch  in  diameter) ;  and  since  each 
fibre  is  capable  of  conveying  an  impression  distinct  from  any  of 
its  fellows,  some  idea  may  be  formed  of  the  perfection  of  the  whole 
arrangement. 

The  sensitive  fibres  are  attached  principally  to  the  skin,  the 
motor  to  the  muscles.  Why?  Because 
the  muscles  being  organs  of  motion 
they  require  nerves  which  will 
convey  the  nervous  stimulus  from 
the  chord  to  them  ;  and  tbe  skin  being 
the  part  upon  which  external  objects 
impinge,  it  requires  nervous  fibres 
capable  of  transmitting  the  impres- 
sions received  by  contact,  from  it  to 
the  chord  and  thence  to  the  brain,  in 
which,  by  the  assistance  of  the  mind, 
they  are  appreciated.* 

How  the  nerves  terminate  is  not 
well  known.  Some  say  in  loops- 
others,  that  they  end  abruptly ;  and 
a  recent  writer  asserts  $  that  in  the 
muscles  they  are  continuous  with 
microscopic  bodies  called  corpuscles. 
It  is  known  that  in  many  parts  of  the 
skin  (fingers,  &c.)  they  end  in  pecu- 
liar, solid,  crow-top-like  structures, 
designated  Pacinian  bodies. 

A  little  reflection  will  unfold  to 
the  reader  the  different  parts  which 
all  the  organs  I  have  been  describing 
play  in  the  living  body ;  and  therefore 
with  the  subjoined  diagram,  expla- 
natory of  the  mode  by  which  sensory 
and  motory  impressions  are  conveyed, 
I  conclude  my  remarks  upon  this 
branch  of  the  subject. 


Skin. 


Muscle. 


PHRENOLOGY. 

As  this  is  a  subject  to  which  much  attention  is  given  by 
the  uneducated  classes  of  society,  and  by  a  few  also  of  those 
who  have  had  opportunities  of  knowing  better,  but  who  love  to  be 
told  by  some  nomadic  vendor  of  characters,  that  they  are  likely  to 
become  Shaksperes,  Miltons,  Newtons,  and  so  forth,  I  think  I  may 

*  It  is  to  be  regretted  that,  at  a  meeting  of  the  British  Association 
two  or  three  years  since,  a  physiologist,  in  communicating  some  exceed- 
ingly original  views  upon  the  distribution  of  motory  and  sensory  nerves, 
confounded  these  with  the  spinal  roots  of  admittedly  compound  nerves, 
and  has  thus  led  his  unscientific  readers  to  form  many  misconceptions. 


124  POPULAR  PHYSIOLOGY. 

conscientiously  say  a  few  words  about  it.  To  the  credit  of  Anglo- 
Saxon  logic,  it  must  be  stated  that  the  science  of  "  bumps  "  did  not 
originate  in  this  country,  but  in  that  which  of  all  others  is  renowned 
for  its  fanciful  generalizations.  There  is  no  need  to  enter  into  the 
doctrines  of  phrenologists,  for  to  those  who  are  already  familiar 
with  them  my  objections  will  be  sufficiently  explicable,  ana  to  those 
who  are  ignorant  of  them  I  would  merely  say,  that  "  ignorance  is 
bliss,"  for  phrenological  wisdom  is  assuredly  the  extremest  folly. 

Objections  to  the  Doctrines  of  Phrenology. 

1st.  It  has  never  been  proved  that  the  human  mind  is  composed  of 
the  several  faculties  which  phrenologists  enumerate. 

2nd.  It  has  never  been  shown  that  any  of  these  faculties  reside  in 
one  particular  convolution,  and  in  no  other. 

3rd.  If  intelligence  be  in  the  grey  matter,  as  phrenologists  admit, 
the  involutions  (foldings  inward)  must  have  faculties  as  well  as 
the  convolutions  ;  yet  as  these  sink  into  the  brain,  no  cognizance 
is  taken  of  them,  though  the  quantity  of  grey  matter  situate  in 
them  is  vastly  greater  than  that  in  the  convolutions. 

4th.  The  most  extensive  convolutions  are  seated  in  the  interior 
and  on  the  base  of  the  brain,  and  are  consequently  never  recog- 
nized by  phrenologists  :  but  these  should  possess  faculties  also, 
and  should  therefore  be  considered  (which  is  impossible)  in 
forming  an  estimate  of  one's  character. 

5th.  The  brain  may  be  elevated  at  some  point  of  the  surface,  and 
phrenologists  would  say  the  faculty  of  this  particular  region  was 
well  developed ;  but  as  the  superficial  part  might  not  have  been 
developed,  but  simply  pushed  up  by  the  development  of  some 
deep-seated  structure,  an  error  may  often  be  fallen  into. 

6th.  Faculties  are  placed  beside  each  other,  though  without  the 
remotest  affinity ;  hence  we  might  reasonably  expect  that  there 
would  be  in  the  brain  a  distinct  line  of  demarcation  between  the 
convolutions  in  which  these  faculties  lie.  But  such  is  not  the 
case ;  one  convolution  passes  insensibly  into  the  other,  like  a 
wave  on  the  sea ;  so  that  it  is  utterly  impossible  to  state  exactly 
where  one  begins  or  l^he  other  ends. 

7th.  There  may  be  a  large  brain,  with  large  convolutions,  yet  from 
the  fact  that  the  involutions  are  shallow,  the  entire  extent  of 
surface  will  be  smaller  than  that  of  an  average  brain,  and  conse- 
quently the  intellectual  power  must  also  be  less. 

8th.  I  have  already  shown  that  the  cerebellum  does  not  preside 
over  the  amatory  passions,  as  is  supposed  by  phrenologists. 

9th.  If  it  be  true  that  each  convolution  represents  a  distinct  faculty, 
then  is  the  common  porpoise  as  highly  gifted  (in  regard  to  the 
number  of  its  faculties)  as  man. 

10th.  Memory  may  be  lost  by  injury  to  any  part  of  the  brain. 

llth.  When  portions  of  the  brain  have  been  removed,  the  mental 
faculties  have  remained  unimpaired. 

12th.  The  convolutions  are  not  symmetrical ;  for  example,  the  con- 


ABSTJKDITIES  OF  PHRENOLOGY.  125 

volution  representing  "hope"  is  not  placed  exactly  opposite 
its  fellow. 

13th.  The  instinctive  faculties  are  possessed  in  the  highest  degree 
by  the  inferior  animals  (invertebrata,  as  insects,  &c.),  which  have 
no  brains. 

14th.  Although  internally  the  skull  forms  a  sort  of  cast  of  the 
convolutions,  yet  externally  this  is  certainly  not  the  case.  The 
skull  is  formed  of  two  layers  of  bone,  with  a  spongey  substance 
between  them ;  the  inner  one  maps  out  the  elevations  of  the 
brain,  but  these  latter  make  no  impression  on  the  outer  one ;  so 
that  where  there  is  an  actual  depression  of  the  brain  there  is 
often  an  external  elevation  of  the  bone,  and  where  the  brain  is 
elevated  it  sometimes  happens  that  the  outside  of  the  skull  is 
flattened. 

15th.  A  case  has  been  lately  recorded  of  a  man,  one  of  whose 
hemispheres  was  completely  destroyed,  and  who,  nevertheless, 
possessed  his  intelligence  intact. 

16th.  M.  Esquirol,  who  has  had,  perhaps,  the  greatest  opportunities 
of  testing  the  truth  of  the  phrenological  doctrines  (having  been 
for  many  years  connected  with  the  most  extensive  lunatic 
asylums  in  Trance),  has  come  to  the  conclusion,  that  in  no  case 
is  phrenology  to  be  depended  on  in  seeking  an  estimate  of  men's 
characters. 

17th.  The  remark  of  Napoleon  to  Las  Casas  may  be  cited  as  a  fair 
objection,  although  there  is  no  bump  of  drunkenness.  Speaking 
of  Gall,  he  observed,  "  He  ascribes  to  certain  prominences  pro- 
pensities and  passions  which  do  not  exist  in  nature,  but  are  the 
growth  of  society  and  merely  conventional.  What  would  the 
organ  of  theft  effect  if  there  were  no  property ;  the  organ  of 
drunkenness,  if  there  were  no  spirituous  liquor ;  or  the  organ  of 
ambition,  if  there  were  no  society  ?  " 

18th.  If  we  were  to  cut  down  through  the  portion  of  the  skull  beneath 
which  phrenologists  suppose  the  faculties  of  colour,  order,  and 
number  to  lie,  we  should  meet  with  a  large  space  between  the 
outer  bone  and  the  inner,  partly  filled  with  loose  spongy  tissue  • 
thus  proving  that  the  prominence  does  not  indicate  any  increased 
development  of  the  parts  of  the  brain  which  are  placed  beneath  it. 

If  the  foregoing  statements,  the  correctness  of  which  is  unde- 
niable, do  not  at  once  banish  from  the  reader's  mind  every  vestige  of 
a  faith  in  phrenology,  I  shall  think  that  conviction  is  impossible.  It 
is  exceedingly  remarkable,  that  the  "amatory  function"  of  the 
cerebellum  was  a  fact  (?)  in  phrenology  which  Spurzheim  believed 
was  supported  by  a  more  overwhelming  mass  of  evidence  than  any 
other.  Alas  !  alas !  poor  phrenology !  If  these  be  thy  surest  props, 
what  becomes  of  thy  other  supports  ?  Must  we  consign  thee,  in 
fellowship  with  mesmerism,  electro-biology,  and  spirit-rapping,  to  the 
hands  of  that  Barnumizing  professor  of  bunkum-science,  the  wan- 
dering Yankee  lecturer  ? 

Ere  we  close  this  chapter,  "  one  last  remark  I  wish  to  make,  one 


126  POPULAR  PHYSIOLOGY. 

last  explanation  I  wish  to  offer/'  in  connection  with  the  skulls  of 
inen,  and  the  period  which  must  have  elapsed  since  man  first  made 
his  appearance  on  the  globe.  The  skulls  of  the  different  nations  of 
the  earth,  though  varying  immensely,  may  yet  be  divided  into  two 
classes,  —  the  long-headed  and  the  round-headed.  In  the  first, 
the  length  from  forehead  to  poll  greatly  exceeds  the  transverse 
width ;  in  the  second,  the  difference  is  less  marked.  In  the  long 
head  the  breadth  is  usually  about  six-tenths  of  the  length ;  whilst 
in  the  round  head  the  transverse  diameter  is,  as  a  rule,  about  nine- 
tenths  of  the  "  fore-and-aft "  measurement.  We  find  the  round 
heads  best  represented  among  the  Turks  and  Tartars,  and  the  long 
heads  among  the  negroes,  whom  I  fear  we  cannot  call  long-headed  in 
any  other  sense.  This  difference  in  the  conformation  of  the  skull, 
however,  does  not  point  to  any  ethical  difference  between  the  cha- 
racters of  the  races  possessing  these  skulls  ;  for,  as  a  distinguished 
palaeontologist  observes,  "  we  may  find  two  races,  such  as  the  Caffre 
and  Calmuc,  with  very  opposite  measurements,  but  yet  very  similar 
in  morals  and  manners,  or  rather  in  the  total  absence  of  both  morals 
and  manners."  Besides  this  distinction  as  to  length  and  breadth, 
there  is  another  and  important  distinction,  with  which  it  is  associated. 
In  some  faces,  such  as  those  of  the  negroes,  we  see  the  face  and  jaw- 
bones projecting  in  advance  of  the  forehead ;  in  others,  on  the  con- 
trary, we  perceive  that  the  face  forms  a  less  or  more  continuous 
right  line  with  the  forehead,  as  in  Europeans.  To  the  first  form  the 
term  "prognathous"  is  applied,  and  to  the  second  the  term  "ortho- 
gnathous ; "  and  it  has  been  found  that  the  prognathous  face  and  long 
skull  are  companions,  and  that  the  orthognathous  face  accompanies 
the  round  head. 

Erom  an  examination  of  the  skulls  of  the  different  peoples  of  the 
world  it  has  been  found  possible  to  draw  a  sort  of  ethnological 
meridian  with  its  two  poles.  Thus,  if  a  line  be  drawn  across  the  map 
of  the  world  from  Russian  Tartary  to  the  Bight  of  Benin  (on  the  south 
coast  of  Guinea),  and  starting  from  its  centre  we  pass  towards  its 
north-eastern  extremity,  we  shall  find  ourselves  among  races  more 
round-headed  and  straight-faced  as  we  approach  the  pole.  If,  on  the 
other  hand,  we  steer  southward,  we  shall  pass  over  a  country  inha- 
bited by  races  with  long  heads  and  projecting  faces,  until  we  arrive 
at  the  southern  pole,  where  these  characters  are  most  prominently 
represented.  This  law  is  possibly  better  established  than^  any  other 
in  the  entire  science  of  ethnology,  and  is  pregnant  with  interest  to 
the  philosophic  mind. 

When  I  ask,  what  is  the  length  of  time  during  which  man  has 
existed  on  the  globe?  I  have  no  doubt  that  many  of  my  fair  readers  will 
reply,  about  five  thousand  five  hundred  years.  Now  it  would  ill  become 
me  to  endeavour,  by  contradiction  merely,  to  shake  one's  faith  in 
generally  assumed  truths;  but  facts  are  never  polite;  there  is.no 
"by  your  leave"  or  "begging  your  pardon"  among  them,  and  as 
everyone  has  a  few  stubborn  friends,  who  will  "  speak  their  minds  " 
in  true  Brummagem  fashion,  I  trust  I  may  be  excused  for  introducing 
some  very  obstinate  fact-acquaintances  of  mine. 


PRE-HISTORIC  AGE   OF  MAtf.  127 

Before  doing  so,  however,  I  must  premise  that  archaeologists  admit 
that,  prior  to  the  great  Roman  nation,  there  lived  upon  the  globe 
two  distinct  races  of  men,  one  of  which  succeeded  the  other. 
The  first  (second  in  point  of  time),  relics  of  which  have  been  found 
pretty  frequently,  were  a  long-headed  people,  and  were  workers  in 
iron.  The  second  were  workers  in  bronze,  but  not  in  iron,  possessed 
some  cultivation,  and  domesticated  animals  for  their  use.  This  last 
race  is  the  earnest  to  which  archaeologist*  can  point. 

Beyond  these,  however,  there  was  another  race,  the  bones  of 
which  have  been  found  associated  with  weapons  of  stone  and  flint, 
but  without  any  remnants  of  domesticated  animals.  To  these  races 
have  been  given  names  taken  from  the  materials  in  which  they 
worked.  Thus  the  first  has  been  called  the  Iron,  the  second  the 
Bronze,  and  the  third  the  Stone  race.  Now  for  our  facts :  "  Denmark 
possesses  great  peat  bogs  in  various  parts  of  the  country,  in  which 
are  embedded  forests  of  trees.  In  the  more  superficial  layers  of  the 
soil  are  embedded  fallen  trunks  of  beech-trees — great  trunks  of  beech, 
like  those  which  now  adorn  the  surface  of  the  country,  and  are  its 
chief  and  most  graceful  decoration.  Beneath  these  beech-trees  we 
come  to  a  lower  forest — a  forest  of  9ak-trees,  fallen,  with  their  tops 
to  the  centre,  of  noble  size — oaks  which  had  taken  centuries  to  grow, 
and  have  been  centuries  in  the  ground.  Dig  deeper  again,  and  you 
come  to  another  forest  of  large  and  splendid  pine-trees — noble  trunks 
of  three  feet  in  diameter,  of  great  age  and  magnificent  proportions. 
Now,  in  the  memory  of  man,  there  has  been,  nothing  in  Denmark  but 
beech-trees,.  Past  the  memory  of  man  grew  and  nourished  those 
giant  oaks ;  they  had  centuries  of  growth,  and  for  centuries  they 
have  been  buried.  Past  these  centuries  we  must  look  down  through 
the  vista  of  ages  for  the  time  when  the  pine-trees  stood  erect,  and 
slowly  gathered  their  bulk,  and  fell  into  the  lowest  part  of  this  deep 
peat,  to  be  again  covered  with  the  wrecks  of  succeeding  epochs  of 
vegetation."  "Now,  in  the  beech  forests  of  the  bog  we  find  only 
traces  of  the  men  of  iron ;  amongst  the  oaks,  only  of  the  men  of 
bronze ;  and  amongst  the  pines,  only  of  the  men  who  worked  in 
stone.  Beneath  the  pines  we  find  only  peat,  and  no  remains  of  man 
of  any  kind  whatever." 

"  What  is  meant  by  this  lapse,  not  so  much  of  time  as  of  facts  ? 
We  cannot  number  the  ages  that  saw  the  rise  and  fall  of  these  monarchs 
of  the  vegetable  world  and  the  succession  of  these  races  of  men."* 

The  foregoing  paragraphs  speak  so  strongly  for  themselves  that 
any  additional  comments  of  mine  would  only  detract  from  their  force. 
There  is  an  old  German  maxim  which  in  this  instance  and  in  all 
similar  ones  is  worthy  of  adoption,  and  as  my  library  does  not  contain 
a  copy  of  Tupper  I  shall,  in  terminating  this  chapter,  quote  it  in  the 
original:— 

"  Reden  1st  Silber,  aber  Schweigen  1st  Gold." 


*  A  lecture  on  the  "  Fossil  Remains  of  Man,"  delivered  at  the  Royal 
Institution,  February  7th,  1862,  by  Professor  Huxley,  F.R.S. 


128  POPULAR  PHYSIOLOGY. 


CHAPTER     XIV. 

Organs  of  Special  Sense — The  Eye— Laws  which  regulate  the  Passage  of 
Bays  of  Light — Refraction  —  Effects  of  Convex  Lenses  on  Light  — 
Spherical  and  Chromatic  Aberration — Form  of  the  Eye — The  Coats 
and  Humours — How  we  see  an  Object — Why  the  Image  is  inverted — 
Why  Bright  Light  and  Darkness  confuse  us  at  first  —  How  we  focus 
the  Eye  —  Short-sight  and  Long-sight  —  Colour-Blindness  —  After 
looking  at  the  Sun  we  behold  a  black  Disk  before  the  Eye — Why  with 
two  Eyes  we  see  but  one  Object — The  Stereoscope  —  Ideas  of  Size, 
Surface,  Form,  Distance,  etc.  —  Eyelids  —  Tears  —  Tear-glands  — 
Diseases  of  the 'Eye. 

HAVING  done  with  the  nervous  system,  viewed  as  a  whole,  and 
having  examined  the  cerebrum,  or  organ  through  which  the  mind 

r rates  in  exhibiting  the  various  mental  faculties,  we  come  now  to 
consideration  of  those  mechanisms  in  which  the  so-called  senses 
are  located.  These  mechanisms  are  the  channels  through  which 
special  impressions  travel  on  their  way  to  the  brain.  Thus,  an  im- 
pression of  light  is  produced  upon  the  inner  portions  of  the  eye,  and 
from  these  passes  to  the  brain,  giving  rise  to  an  idea  of  the  object 
seen.  Likewise,  in  the  cases  of  hearing,  taste,  smell,  and  touch,  im- 
pressi9ns  are  conveyed  to  the  cerebrum,  and  ideas  in  connection  with 
these  impressions  are  developed.  In  this  manner  we  may  regard  the 
brain  as  a  sort  of  mental  stomach,  with  which  are  connected  a  series 
of  mouths  (organs  of  sight,  smell,  taste,  touch,  and  hearing).  Through 
these  mouths  the  crude  food  which  is  taken  in  is  carried  to  the  brain, 
and  is  there  in  the  form  of  ideas,  of  a  loose,  heterogeneous  type.  The 
brain  (through  the  assistance  of  the  mind)  associates  these  mingled 
notions,  arranges  them  in  bundles,  and  thus  the  mental  power  is  in- 
creased by  (as  it  were)  a  species  of  cerebral  digestion.  We  have 
now  arrived  at  the  senses,  and  before  we  commence  the  study  of  any 
one  of  them  it  behoves  us  to  inquire  whether  there  is  any  character 
common  to  all,  so  that  we  may  catch  it,  and  form  a  general  idea  of  a 
sense.  There  is  a  common  feature,  viz.,  each  sense-organ  consists  of 
two  very  distinct  portions,  which  may  be  termed  the  receptive  and 
perceptive  regions  respectively.  In  the  ear  we  find  a  complex  appa- 
ratus for  the  reception  of  the  vibrations  of  the  air  which  produce 
sound;  and,  in  addition,  we  observe  an  arrangement  of  a  nervous 
nature,  by  which  the  vibrations  are  perceived,  and  then  carried  to 
the  brain.  The  same  thing  may  be  said  of  the  tongue,  the  nose,  the 
skin  of  the  fingers,  and  the  eye,  of  which  we  propose  to  investigate 
the  structure-  and  function  in  this  chapter. 

We  say  this  man  sees  quite  distinctly,  but  that  P9or  fellow  is 
blind.  The  one  can  make  his  way  onward  without  coming  into  col- 
lision with  external  objects,  the  other  cannot.  Again,  no  man  can 
walk  without  danger,  in  perfect  darkness,  or  with  his  eyes  closed. 


HOW  LIGHT   TRAVELS. 


129 


These  facts  prove  two  or  three  important  things;  they  show  us, 

Firstly,  that  we  only  become  cognizant  of  the  existence  of  external 
and  surrounding  objects  through  the  action  of  the  eye  •  and — 

Secondly,  that  the  eye  recognizes  these  objects  through  the  in- 
fluence of  light. 

Therefore,  in  order  fully  to  understand  the  mode  in  which  vision  is 
effected,  we  must  make  ourselves  acquainted  with  the  structures  of 
the  eye,  and  also  with  the  properties  of  light  and  the  laws  by  which 
its  rays  are  governed  ;  in  fact,  we  must  learn  a  little  of  that  difficult 
branch  of  knowledge — optics. 

Light  passes  from  the  body  which  emits  it  in  straight  lines.  A  ray 
of  light  travelling  from  the  sun 
to  the  eye  pursues  a  rectilinear 
course.  If,  however,  on  its  journey 
it  has  to  pass  obliquely*  through 
some  medium  of  a  density  different 
from  that  of  the  atmosphere,  it 
will  have  its  path  broken,  and 
will  travel  to  the  earth  in  another 
direction.  This  process  by  which 
the  ray  is  diverted  is  termed  re- 
fraction. 

If  a  ray  of  light  (p  /)  which 
has  travelled  from  the  sun  strike 
obliquely  a  plate  of  _  thick  glass 
(a  be  d],  instead  of  passing  onwards 
directly  in  a  line  {fgl}  with  its 
path  from  the  sun,  it  will  be  turned 
more  to  the  left  (/  K),  and  so  will  travel  through  the  plate  till  it 
reaches  the  other  side  (h) ;  here,  as  it  emerges  from  the  glass,  its 
course  is  again  changed,  and  it  is  bent  towards  the  right  (h  h'}.  If, 
then,  a  perpendicular  line  (o  i)  had  been  drawn  at  the  point  of 
entrance  of  the  ray,  we  should  have  found  that  this  latter  was  bent 
towards  it  as  it  travelled  through  the  glass,  and  from  it  on  emerging. 

It  is  upon  this  known  property  of  glass  (and  such-like  dense  transpa- 
rent substances)  that  the  formation  of  images  by  lenses  depends.  You 
know  that  if  a  lens  (double  convex)  be  fixed  in  a  hole  in  the  shutter 
of  a  window  and  the  shutter  closed,  a  sheet  of  white  paper  placed 
at  some  distance  from  the  lens  will  have  formed  on  it  a  distinct  picture 
of  everything  which  is  in  front  of  the  window.  This  is  explained 
as  follows.  Let  the  arrow  a  b  (fig.  75)  be  placed  in  front  of  the  lens 
c  d,  and  let  ef  represent  a  screen  placed  behind  for  the  reception  of 
the  image.  The  rays  of  light  passing  from  the  ends  of  the  arrow 
will  impinge  upon  the  edges  of  the  lens,  and  will,  by  refraction,  be 

*  Kays  which  fall  vertically  upon  a  medium,  such  as  glass,  are  trans- 
mitted in  the  same  line,  and  consequently  suffer  no  refraction  ;  but  other 
things  being  the  same,  the  more  obliquely  a  ray  falls  (on  a  lens,  for  in- 
stance), the  greater  will  the  refraction  be. 

K 


130 


POPULAR  PHYSIOLOGY. 


caused  to  converge  as  they  leave  these  edges ;  therefore  they  will 
meet  it  at  a  certain  point.  But  this  is  not  all.   They  then  cross  each 


Fig.  75. 

other,  diverge,  and  at  length  form  an  image  (which  is  inverted}  on 
the  screen.  That  the  image  is  inverted  will  be  readily  believed  by  all 
who  understand  photography. 

The  reason  why  a  lens  is  so  shaped,  is  in  order  that  the  rays  which 
proceed  from  the  edges  of  an  object  may  be  caused  to  converge,  and 
thus  all  the  rays  be  brought  to  one  point,  which  is  called  the  focus.  If  it 
be  not  at  first  clearly  understood  why  the  rays  converge,  let  lines  be 
drawn  perpendicular  to  both  surfaces  of*  the  lens,  and  then  let  it 
be  remembered  that  oblique  rays,  when  passing  into  a  denser  from  a 
rarer  medium  are  bent  towards  the  perpendicular,  and  when  entering 
a  rarer  medium  are  bent  from  the  perpendicular,  and  the  process  will 
at  once  be  intelligible. 

It  sometimes  occurs  that  all  the  rays  of  light  coming  from  an  object 
do  not  meet  at  one  point  after  they  have  travelled  through  a  double 
convex  lens ;  the  rays  which  fall  upon  the  edges  converge  at  a  greater 

distance  from  the  glass  than 
those  which  traverse  the  cen- 
tral portion ;  hence  there 
results  a  confused  image, 
and  this  defect  is  termed 
"  spherical  aberration."  It 
is  corrected  by  having  the 
surface  of  the  lens  curved  in 
such  a  manner  that  all  the 
rays  are  caused  to  meet  in 
one  focus. 

There  is  another  defect, 
Fig.  76  which  manjr  lenses  exhibit, 

and  which  is  called  "chro- 
matic aberration;"  and  which  consists  in  the  display  of  various 
colours  besides  those  of  the  object  from  which  the  rays  of  light 


SPHERICAL  AXD  CHROMATIC  ABERRATION. 


131 


travel.  In  order  to  explain  this  phenomenon  I  must  tell  you  that 
white  light — that  of  the  sun,  for  example — is  really  composed  of  three 
distinct  colours  :  red,  blue,  and  yellow.  We  can  prove  this  in  the  fol- 
lowing manner.  Let  a  stream  of  light  (fig.  76),  reflected  from  a  mirror 


Fig.  77. 

(m),  pass  through  an  aperture  in  the  side  of  a  dark  chamber,  and  it 
will  produce  a  circular  spot  of  white  light  (g).  If,  however,  a 
glass  prism  (p)  be  interposed,  the  rays  will  be  refracted  towards  r  uy 
and  as  the  colours  which  together  constitute  white  light  are  broken 


132 


POPULAR  PHYSIOLOGY. 


at  different  angles, 
and  thus  separated 
from  each  other,  we 
shall  have  at  r  u  a 
spectrum  or  row, 
which,  like  a  rainbow, 
contains  the  primary 
shades ;  these  latter 
being  called  pris- 
matic colours,  be- 
cause produced  by 
the  action  of  a.  prism. 
Now  this  property 
of  prisms  is  also  pos- 
sessed by  many 
lenses,  and  hence 
with  such,  true  im- 
ages cannot  be 
formed.  This  "chro- 
matic aberration"  or 
tendency  in  glasses 
to  decompose  white 
light,  is  corrected  by 
combining  together 
lenses  of  different 
densities,  which  are 
then  called  "  a-chromatie"  or 
non-colour-forming,  and  these 
are  invariably  the  more  expen- 
sive forms. 

We  are  now  in  a  position  to 
enter  upon  the  subject  of  the 
eye  itself.  It  has  been  said 
that  the  human  organ  of  vision 
is  the  most  perfect  optical  ap- 
paratus that  can  be  conceived. 
This  is  not  the  case;  for  although 
its  defects  are  exceedingly 
slight  and  unimportant,  yet, 
nevertheless,  they  are  defects. 

The  eye  (A,  fig.  77)  is  of  a 
spheroidal  form,  and  is  fixed  in 
a  niche  or  socket,  formed  by 
the  union  of  several  bones.  It 
can  be  moved  either  in  or 
out  (n  i],  up  or  down  (s), 
or  may  be  made  to  rotate 
upon  its  front-to-back  axis  (o  c) 
by  means  of  muscles,  six  in 
number,  which  are  attached  to 


COATS  OF  THE  EYE.  133 

its  outer  surface,  and  also  to  the  bony  socket.  It  is  composed 
of  several  coats  of  membrane,  which  overlie  each  other  like  the 
skin-laminae  of  an  orange,  and  of  certain  lenses,  or  humours,  which 
are  contained  within  these  coats.  The  optic  nerve  enters  it  behind, 
and  spreads  internally  in  the  form  of  a  layer  which  is  termed  the 
retina.  I  may  here  mention  that  the  optic  nerves,  prior  to  their 
entrance  into  the  eyes,  decussate,  or  cross  each  other,  and  in  doing  so 
allow  their  fibres  to  intermingle,  so  that  each  eye  contains  fibres 
from  the  two  nerves,  as  shown  in  fig.  77. 

The  outer  surface  of  the  eye  is  white,  save  at  one  place  in  front, 
which  is  beautifully  transparent,  and  through  which  the  rays  of  light 
travel  on  their  way  to  the  inner  portions  of  the  ball.  The  wall  of  the 
eye  is  composed  of  three  coats,  named  from  without  inwards,  the 
sclerotic,  the  choroidi  and  the  retina. 

The  sclerotic,  or,  as  it  is  more  frequently  styled,  "the  white  of  the 
eye,"  is  a  tough,  dense,  fibrous  tunic,  which  entirely  invests  the  eye, 
except  at  the  locality  alluded  to— the  cornea  (A  A,  fig.  79).  It  con- 
stitutes about  four-fifths,  and  the  latter  structure  the  remaining; 
one-fifth,  of  the  entire  surface  of  the  eyeball.  Its  beautifully  smooth 
and  glistening  appearance  is  due  to  a  delicate  layer  of  mucous 
membrane,  which  clothes  its  entire  surface,  is  continued  over  the 
cornea,  and  also  over  the  internal  surface  of  the  eye-lids. 


Fig.  79. 

The  cornea  (B) — which  we  may  regard  as  the  clarified  transparent 
portion  of  the  sclerotic— bulges  out  a  little  from  the  eyeball.  It  is,  in 
fact,  a  sort  of  watch-glass,  fitted  into  the  sclerotic,  which  contains  a 
kind  of  groove  into  which  the  cornea  is  inserted.  It  is  composed  of 
different  layers,  two  of  which — the  inner  and  outer — are  very  elastic. 
As  these  are  of  more  interest  to  the  miscroscopic  anatomist  than  to 
the  physiologist,  we  shall  not  dwell  upon  them  further.  No  blood- 
vessels can  be  discovered  in  the  cornea ;  indeed,  it  is  evident  that  if 
blood-vessels  were  present,  much,  if  not  all,  of  its  transparency 
would  be  lost.  But  although  no  channels  large  enough  for  the  con- 
veyance of  the  red  particles  of  the  blood  exist,  there  are  minute 
passages  through  which  the  purely  fluid  elements  may  be  conveyed.* 

*  This  has  been  questioned  by  some  writers. 


134  POPULAR  PHYSIOLOGY. 

The  choroid  coat  (T  T)  is  composed  of  hundreds  of  blood-vessels,  and 
minute  polygonal  bodies  containing  black  pigment  or  colouring 
matter.  It  fines  the  whole  of  the  internal  surface  of  the  sclerotic, 
from  the  entrance  of  the  optic  nerve  behind,  to  the  junction  of  the 
former  with  the  cornea  in  front,  and  is  continued  over  the  back  part 
of  an  organ  we  shall  come  to  presently — the  iris  (n).  The  use  of  the 
choroid  is  by  some  considered  to  be  to  preserve  the  warmth  of  the 
retina,  which  lies  within  it.  This  is  not  its  only  object ;  its  black 
pigment  absorbs  all  the  loose  rays  of  light,  thus  prevents  their 
reflection  from  one  side  of  the  eye  to  the  other,  and  therefore  tends 
to  render  images  less  confused.  It  fulfils  the  same  office  as  the 
black  lining  to  the  tube  of  a  microscope,  and  when  absent — as  in 
albinoes— the  eye  is  unable  to  perceive  objects  placed  in  a  very 
bright  light.  The  development  of  this  pigment  in  the  eye  is  pro- 
portioned to  its  development  in  other  portions  of  the  body — hair,, 
skin,  &c. :  hence,  those  who  have  fair  hair  have  light  blue  eyes,  and 
those  with  a  swarthy  skin  have  black  eyes ;  also,  those  who  have 
black  eyes  can  tolerate  a  more  glaring  light  than  those  who  have 
eyes  of  a  grey  or  azure  tint. 

The  Retina. — This  is  the  nervous  layer  of  the  eye  (R  R)  ;  it  is  the 
expansion  of  the  optic  nerve,  and  lies  immediately  within  the  choroid, 
which  can  be  seen  behind  it  because  of  the  transparency  of  the 
latter.  It  consists  of  several  layers  of  cells,  fibres,  granules,  and 
rods,  which  are  placed  one  over  the  other,  and  can  only  be  seen  with 
the  assistance  of  the  microscope.  The  retina  is  the  "  collodion 
plate "  of  the  eye,  upon  which  is  photographed  the  multitude  of 
objects,  which  are  hourly  and  almost  incessantly  presented  to  the 
mind.  Extending  as  it  does  over  the  whole  inner  surface  of  the  ball 
as  far  almost  as  the  iris,  it  constitutes  a  vast  canvas  for  the  reception 
of  images,  and,  although  extremely  sensitive  to  light*  at  every  point 
but  one,  there  is  one  locality  in  which  impressions  are  received  more 
distinctly  than  in  others,  and  one  place  where  there  exists  no  sensa- 
tion at  all,  and  which  is  commonly  designated  "  the  blind  spot." 
The  portion  of  the  retina  which  is  capable  of  receiving  the  most 
delicate  impressions  is  situate  in  the  front-to-back  axis,  or  rather  in 
the  hinder  pole  of  this  axis.  It  is  the  spot  upon  which  the  rays  of 
light  most  usually  impinge,  and  it  has  been  said  that  to  ensure  perfect 
vision  the  image  must  be  formed  upon  this  region.  The  blind  point 
lies  at  the  entrance  of  the  optic  nerve.  This  latter  enters  the  eyeball 
not  in  the  centre  of  its  back  portion,  but  at  a  point  nearer  the  inner 
surface  ;  hence  it  is  not  often  t  so  placed,  that  images  are  thrown 
upon  it.  The  following  experiment  demonstrates  its  existence. 
Holding  the  arms  out  at  full  length,  bring  the  two  thumbs  upwards 
and  together ;  then,  having  closed  the  left  eye,  regard  the  left  thumb 
fixedly  with  the  right  eye,  and  while  doing  so  slowly  move  outwards 
the  right  arm,  and  the  right  thumb  will,  in  passing,  become  invisible 


*  I  have  italicised  the  word  light,  because  some  persons  might  suppose 
that  it  was  also  capable  of  feeling  pain  ;  but  this  is  not  the  case. 


HUMOURS  OF  THE  EYE.  135 

at  one  particular  point,  viz.,  as  the  image  passes  over  the  "  punctum 
caecum"  The  retina  ends  in  front  by  a  toothed  border,  which  dove- 
tails with  the  choroid  at  a  short  distance  from  the  union  of  the 
sclerotic  and  cornea. 

The  next  question  that  suggests  itself  is,  what  is  to  be  found 
within  these  coats  ?  Looking  upon  the  eye  as  a  sort  of  capsule, 
we  may  for  convenience  of  description  divide  it  into  two  portions — 
back  and  front.  These  are  filled  with  materials  of  different  cha- 
racters; those  which  are  contained  in  the  posterior  part  being 
solid,  and  those  in  front  more  or  less  fluid.  The  great  bulk  of 
the  eye  belongs  to  the  hinder  division,  and  comprises  two  distinct 
structures,  which  are  perfectly  transparent, — the  Vitreous  Humour, 
and  Crystalline  Lens.  And  first  of  the  Vitreous  Humour  (y) : 
this  is  a  clear,  solid,  jelly-like  mass,  closely  embraced  behind  and  at  its 
sides  by  the  retina.  It  fills  the  ball  from  behind,  to  about  the  com- 
mencement of  the  cornea  in  front  (where  it  is  overlapped  by  the 
termination  of  the  choroid),  and  is  enclosed  in  a  membranous  bag 
which  enters  the  humour,  and  divides  it  into  numerous  compart- 
ments. 

The  lens,  or  crystalline  lens  (c),  is  placed  just  in  front  of  the 
vitreous  humour,  in  a  hollow,  _  which  the  latter  presents  for  its 
reception.  It  is  a  very  small,  lenticular  body,  double  convex, — that  is, 
elevated  on  both  sides,  and  transparent ;  moreover  it  does  not  merely 
lie  in  the  depression,  but  is  fixed  in  its  proper  position  by  a  circular 
band,  which  is  attached  on  the  one  hand  to  the  membrane  which  encloses 
the  lens,  and  on  the  other  to  a  sinewy  fold,  which  passes  around  within 
the  eye  at  the  union  of  _  sclerotic  and  cornea.  It  is  much  flatter  in 
front  than  behind,  and  is  composed  of  about  200  layers  of  fibres, 
which  are  toothed  at  the  edges,  and  adapted  to  each  other  beauti- 
fully. In  front  of  the  crystalline  lens  and  the  vitreous  humour 
(which  united  fill  up  the  whole  of  the  back  part  of  the  eyeball),  and 
behind  the  cornea, — intervening  between  the  two,  is  a  cavity,  which 
during  life  encloses  a  fluid  of  a  saline,  transparent  character— the 
Aqueous  Humour  (D).  I  have  nothing  more  to  say  concerning  this 
humour,  save  that  it  is  almost  divided  into  two  portions  by  an 
exquisite  circular  partition,  which  has  an  aperture  in  its  centre.  This 
partition  is  named  the  Iris  (i  i),  and  in  it  lies  the  colouring  matter 
which  gives  the  peculiar  shade  either  of  brown,  hazel,  blue,  or  grey,, 
to  which  much  of  the  beauty  of  the  eye  is  due.  The  small  aperture 
is  called  the  Pupil,  and  is  recognised  as  a  black  spot  in  the  centre  of 
the  eye,  which  increases  in  size  in  the  shade,  and  diminishes  under 
the  influence  of  light. 

How  does  this  circular  aperture  get  smaller  or  larger?  By 
changes  in  the  iris.  The  latter  contains  two  distinct  ^sets  of 
muscular  fibres ;  one  series  is  disposed  in  concentric  rings  or 
circles,  and  when  they  contract,  the  orifice  (pupil)  is  diminished.  The 
second  series  is  arranged  in  a  radiating  manner,  in  other  words  the 
fibres  pass  out  from  the  central  to  the  circumferential  parts  as  spokes 
from  the  middle  of  a  wheel,  and  when  shortened  during  contraction 
they  tend  to  widen  or  dilate  the  orifice,  giving  a  very  brilliant  appear- 


136  POPULAR  PHYSIOLOGY. 

ance  to  the  eye.*  Finally,  the  iris  is  lined  at  the  back  by  a  continuation 
of  the  choroid  coat,  and  therefore  it  forms  an  opaque  shutter  for  the 
sensitive  surface  of  the  retina.  There  is  yet  another  structure  which 
had  almost  escaped  our  notice, — this  is  ciliary  muscle ;  it  consists  of 
a  belt  or  zone  of  muscular  tissue,  which  is  attached  to  the  cornea 
and  sclerotic  at  their  junction,  and  which  passes  round  the  whole  eye 
in  this  region  (L  L).  It  is  also  united  at  its  inner  border  to  the  crystal- 
line lens,  and  some  physiologists  believe  that  it  is  the  special  muscle  of 
this  body. 

The  exact  office  of  each  of  the  mechanisms  we  have  been  studying 
will  be  explained  in  replying  to  the  following  {questions : — 

How  do  we  see  an  object  ? — I  think  the  reader  is  now  in  a  fair  position 
to  answer  this  question.  The  rays  of  light  (ag,  b  t,  fig.  78)  which  come 
from  an  object,  strike  upon  the  cornea  (d  e],  and  as  it  is  transparent 
they  travel  through  it,  but  in  doing  so  they  are  bent  from  their  former 
direction  and  caused  to  converge.  Now,  forming  a  cone,  they  pass 
together  through  the  aperture  of  the  iris  (the  pupil),  impinge  upon 
the  crystalline  lens  (n  op  q),  and  are  transmitted,  but  are  forced 
t9  converge  still  more,  till  they  meet  at  a  point  (r)  somewhere  in  the 
vitreous  body.  This  is  the  focus,  and  from  it  they  then  diverge,  and 
at  last  strike  the  retina ;  so  that  in  this  manner  a  picture  (ufo)  is 
thrown  upon  it.  Strange  to  say,  however,  this  picture  is  turned 
upside  down,  for,  as  the  rays  ^Verged  after  their  convergence,  those 
which  came  from  the  top  of  the  object  passed  downwards,  and  those 
from  the  bottom  upwards. 

How,  then,  do  we  seethe  object,  as  if  the  image  on  the  retina  was  not 
inverted? — This  question  has  been  answered  by  many  writers.  One 
tells  us  it  is  certainly  because  of  one  circumstance ;  and  another  lays 
down  the  law  with  apparently  equal  force ;  but,  somehow  or  other, 
a  little  consideration  will  invariably  enable  the  reader  to  detect  a 
blunder  in  the  explanation.  For  myself,  I  am  content  to  say  I  do 
not  understand  the  reason,  though  I  admit  the  fact ;  and  that,  till 
some  one  points  out  a  more  intelligible  cause  than  those  already  put 
forward,  I  must  think  that  the  correction  is  due  to  some  influence  of 
the  mind,  which  at  present  we  are  unable  to  comprehend. 

Why  cannot  we  at  first  see  distinctly,  when  we  encounter  a  bright  light 
after  having  been  for  some  time  in  the  dark  ?  And  why,  when  we  pass 
from  the  bright  sunlight  into  a  dark  cellar,  are  we  for  a  few  moments 
confused? — I  have  given  these  two  questions  together,  for  their 
answers  bear  much  upon  each  other.  In  the  first  instance,  we  have 
been  in  a  dark  chamber,  and  in  order  to  see  as  clearly  as  possible,  our 
pupils,  or  passages  for  the  entrance  of  light,  have  been  opened 
widely.  On  entering  the  well-lit  room,  the  light  enters  too  freely 
by  the  enlarged  orifice ;  and  so  things  are  seen  dimly,  or  we  close 
our  eyes  for  a  few  moments.  This  unpleasant  sensation  does  not 
last  long,  for  the  iris,  by  contracting,  diminishes  the  aperture, 

*  If  a  drop  of  a  solution  of  atropia  is  placed  upon  the  eyeball,  a 
similar  effect  is  produced  in  a  very  short  time.  This  fact  is  so  well 
known  to  many  members  of  the  fair  sex  that  I  merely  allude  to  it  without 
further  comment. 


OPTICAL  PHENOMENA  OF  EYE.  137 

regulating  its  size;  and  thus  only  the  proper  quantity  of  light 
is  admitted.  In  answering  the  second  question,  I  need  only 
say  that  the  pupil,  which  was  diminished  in  size  by  the  influence 
of  the  sun-light,  was  not  sufficiently  large  on  entering  the  cellar 
to  admit  light  enough  for  objects  to  be  seen  at  all. 

That  this  proportioning  of  the  size  of  the  pupil  to  the  brightness  of 
the  light  does  take  place,  the  reader  may  demonstrate  for  himself  by 
examining  the  size  of  the  pupil  (under  different  conditions)  with  the 
assistance  of  a  small  mirror.  The  iris,  then,  constitutes  the  shutter  of 
the  eye,  and  protects  the  sensitive  retina  from  the  baneful  influence  of 
excessive  light.  Its  alternate  contractions  and  relaxations  are  very  good 
examples  of  what  are  termed  reflex  actions.  Without  any  attempt  at 
what  a  distinguished  author  has  termed  Bridgewater-writing"  I  think 
we  may  well  regard  the  iris  as  one  of  those  innumerable  evidences 
of  the  existence  of  that  "  high  and  mighty  King  of  Kings  "  which 
biology  offers  to  the  mind  of  the  reflective  student. 

Why  are  we  at  first  imable  to  perceive  a  distant  object,  when  for 
some  time  previously  we  have  been  regarding  a  near  one?  And  why, 
after  we  have  been  looking  at  something  in  the  distance,  are  we 
unable  at  first  sight  to  perceive  clearly  any  object  which  is  placed 
near  the  eye  ?  The  first  tiling  which  these  two  questions  suggest  is, 
that  the  eye  has  the  power  of  adapting  itself  to  near  and  distant 
objects,  so  that  each  may  be  observed  distinctly.  If  the  eye  remained 
unchanged  as  regarded  the  curves  of  its  constituent  lenses,  the  rays 
from  distant  objects  would  n9t  be  focused  at  the  same  point  as  those 
of  near  ones ;  consequently,  either  set  would  be  perceived  indistinctly. 
How  the  eye  does  change  the  form  of  its  lenses,  and  what  lenses  are 
altered,  are  questions  which  have  been  answered  over  and  over  again, 
and  whose  answers  [as  given  by  physiologists]  are  of  the  most  con- 
flicting kind.  Quite'  recently,  a  writer  has  asserted  that  the  blood- 
vessels, by  the  pressure  which  they  exert  on  the  vitreous  humour, 
cause  this  to  be  projected  forwards  *"  as  a  patient  is  on  a  water-bed," 
and  therefore  the  lens  to  be  advanced  also;  and  that  this  change 
always  takes  place  when  we  view  a  near  object.  Unfortunately  for 
this  theory  (which,  by  the  way,  is  not  by  any  means  a  recent  one),  it 
is  known, — * 

Firstly, — That  there  is  an  aqueous  humour  between  the  iens  and 

cornea,  and  that  in  order  that  these  should  be  advanced  it  should 

be  allowed  to  escape. 
Secondly,— That  in  all  cases  of  congestion  of  the  eye  there  is  not 

an  absence  of  "  distant  vision  ;"  and 
Thirdly,— That  the  retina  might  not  be  able  to  sustain  such  severe 

pressure. 

A  glance  at  the  construction  of  the  eyeball  will  give  the  reader  an 
insight  into  the  true  process  of  "  adaptation,"  as  it  is  called.  Look 
at  the  position  of  the  ciliary  muscle — a  structure  which  (as  has  been 
demonstrated  in  the  eyes  of  birds)  is  undoubtedly  contractile,  and 

*  For  my  objections  to  this  hypothesis  consult  the  "  British  Medical 
Journal"  for  April  18th,  1863. 


138  POPTJLAE  PHYSIOLOGY. 

you  will  perceive  that,  situated  as  it  is,  a  very  slight  contraction  of 
its  fibres  must  produce  a  constriction  of  that  part  of  the  "ball"  at 
the  junction  of  the  sclerotic  and  cornea.  Now,  what  will  be  the  im- 
mediate result  of  this  constriction  ?  Simply,  a  bending  inwards  (all 
round)  of  the  hinder  border,  or  edge  of  the  cornea.  What  will  be 
the  effect  of  this  ?  An  increased  curvature  of  the  cornea,  and  hence 
the  capability  on  the  part  of  the  eye  of  perceiving  near  objects.  Let 
us  suppose  that  it  is  required  to  examine  a  very  distant  object.  What 
happens  then  ?  The  muscle  relaxes,  and  the  cornea,  by  virtue  9f  its 
elasticity,  which  is  very  great,  returns  at  once  to  its  former  position. 
That  the  iris  has  nothing  to  do  with  either  near  or  distant  vision  has 
been  shown  in  a  case  recorded  by  a  great  German  surgeon.  _  The 
patient  had  had  his  iris  completely  removed,  yet  his  power  01  perceiving 
near  and  distant  objects  remained  the  same  as  it  had  been  before  the 
operation. 

The  above  explanations  lead  us  to  another  question, —  Why  are 
some  people  short-sighted  and  others  long-sighted  ?  In  near-sighted 
people f  the  cornea  is  extremely  convex;  hence  its  power  of 
refraction  is  very  great,  and  the  rays  are  brought  to  a  focus  too 
soon  to  allow  of  "distant  objects  being  seen  distinctly.  If  therefore 
we  can  by  any  means  bring  the  rays  coming  from  a  distant  body  in 
such  a  manner  that  they  shall 'strike  the  cornea  more  obliquely,  they 
will  not  be  brought  to  a  focus  so  soon,  but  will  form  a  clear  image  on 
the  retina.  Concave  glasses  produce  this  eifect,  and  consequently 
these  are  the  kind  employed  in  the  spectacles  of  near-sighted  persons. 
In  long-sighted  people  the  cornea  is  too  flat,  and  the  rays  are  not 
brought  to  a  focus  soon  enough— the  image  having  a  tendency  to  be 
formed  behind  the  retina.  This  results  from  the  rays  not  falling  per- 
pendicularly enough  to  be  refracted  sufficiently ;  and  therefore  we 
add  to  the  ordinary  refractile  power  of  the  eye  by  placing  a  convex 
lens  in  front  of  it.  That  long-sighted  people  have  flat  corneas,  and 
short-sighted  persons  prominent  ones,  I  think  is  evident  to  every  one 
who  possesses  even  ordinary  observation. 

Why  are  some  objects  one  colour,  and  others  another?  I  told 
you  before:  that  white  light  is  really  composed  of  many  distinct 
hues  ;  and  as  we  see  all  things  by  the  aid  of  light  which  is  reflected 
from  them,  it  follows  that  if  any  body  or  object  absorbs  some  of  the 
coloured  rays  completely,  only  the  remaining  ones  will  be  reflected  to 
the  eye  and  be  recognized.  Thus  anything  which  absorbs  all  the  red 
rays  will  appear  green,  an  object  will  appear  blue  which  retains  the 
red  and  yellow  rays,  and  so  on. 

It  is  extraordinary,  that  in  some  individuals  the  power  of  appre- 
ciating certain  colours  is  not  present.  There  are  persons  who  cannot 
distinguishbetweenblueand  scarlet.  This  peculiarity  is  termed  "colour- 
blindness," and  is  much  more  prevalent  than  it  is  thought  to  be  by 
many. 

It  is  stated  that,  on  one  occasion  a  tailor  sewed  together  the 
different  portions  of  a  scarlet  hunting-coat  with  blue  silk,  and  pre- 
sented it  to  his  master  with  the  utmost  gravity,  having  been  unable 
to  detect  his  error,  by  reason  of  his  inability  to  discriminate  between 


COLOUR-BLINDNESS — THE  STEREOSCOPE.  139 

the  two  colours,  scarlet  and  blue.  If  we  gaze  fixedly  and  for  some 
time  upon  a  piece  of  scarlet  paper,  and  then  turn  the  eye  upon  some 
other  object,  it  appears  of  a  greenish  hue.  How  is  this  ?  The  retina 
having  been  exerted  in  staring  at  one  colour,  at  length  becomes  in- 
sensible to  it,  and  is  capable  of  receiving  only  the  two  other  colours 
(blue  and  yellow*),  hence  everything  looks  green. 

This  explanation  enables  us  to  understand  the  cause  of  another 
phenomenon,  which  is  this  :  if  after  looking  upon  the  sun  we  turn 
our  eyes  upon  some  other  object,  we  observe  a  round  black  spot.  In 
this  case,  that  part  of  the  retina  which  has  received  the  direct  rays 
has  become  pro  tempore  paralysed,  and  when  we  regard  other  objects, 
they  are  depicted  on  every  portion  of  the  recipient  surface  except  the 
insensible  round  spot,  which  then  appears  as  a  black  disk  on  the  field 
of  vision. 

Having  two  eyes,  we  have  simultaneously  formed  two  distinct 
images  of  every  object :  why  then  do  we  not  see  things  double? 
Because  the  mind  associates  the  images,  and  when  two  of  them  are 
depicted  on  the  retina,  the  mind  by  habit  perceives  but  one.  That 
the  perception  of  a  single  object  is  in  a  great  measure  the  result  of 
habit,  appears  from  the  fact  that  when  we  press  one  of  the  eyeballs 
inwards,  and  so  cause  an  image  to  fall  upon  a  part  of  the  retina, 
which  has  not  acquired  the  property,  a  double  picture  is  seen.  In 
squinting  also,  where  the  rays  are  thrown  upon  a  new  portion  of  the 
retina,  double  vision  results,  but  after  some  time  objects  are  seen  as 
usual. 

Some  physiologists  tell  us,  that  without  the  two  eyes  we  could 
form  no  conception  of  solidity:  this  is  not  true.  Close  one  eye, 
and  with  the  other  you  gain  nearly  as  perfect  notions  of  the  solidity 
of  a  box,  a  table  or  a  bottle,  as  you  did  with  the  two.  However, 
there  is  no  doubt  that  we  do  get  with  the  two  eyes  different  views  of 
the  same  object.  Look,  for  example,  at  the  back  pf  a  thin  book 
which  is  held  on  a  line  with  the  nose,  and  at  a  short  distance  from  it, 
first  with  one  eye,  and  then  with  the  other ;  and  you  will  perceive 
that  you  have  seen  it  from  different  points  of  view.  In  looking  at  it 
with  both  eyes,  it  is  supposed  that  the  mind  summing  up  the  two 
aspects  has  concluded  that  the  object  is  solid,  in  the  same  way 
as  a  person  who  has  seen  two  sides  of  one  of  the  pyramids  of 
Egypt  forms  an  idea  of  its  solidity,  whilst  had  he  been  placed  at  once 
in  front  of  but  one  side,  he  would  have  thought  it  but  a  gigantic  wall. 
In  the  stereoscope,  two  pictures  9f  a  relief  are  placed  beneath  the 
eyes,  and  they  are  perceived  as  a  single  picture  which  "  stands  out  " 
perfectly.  This  will  not  be  the  case  if  the  pictures  be  merely  similar 
ones ;  they  must  represent  the  images  which  would  be  formed  upon 
the  two  retinae  when  the  object  itself  was  viewed.  In  other  words, 
they  must  be  taken  from  different  points  of  view ;  one  must  be  the 
picture  as  it  would  be  seen  by  the  right  eye,  and  the  other  such  as 
would  be  projected  upon  the  retina  of  the  left. 

*  These  are  then  termed  "complementary"  colours,  as  they  are  portions 
of  the  white  light.  Red,  blue,  and  yellow  are  complementary  to  each 
other. 


140  POPULAR  PHYSIOLOGY. 

When  a  burning  Irand  is  icaved  violently  to  and  fro,  why  do  we 
perceive  a  tape-like  flame,  in  the  form  of  a  circle  ?  An  image  which 
has  been  formed  upon  the  retina  remains  for  about  the  one-tenth  of  a 
second,  and  after  that  vanishes.  If,  then,  we  can  throw  upon  the  sen- 
sitive surface  a  series  of  images  of  the  same  object  within  the  one- 
twentieth  of  a  second,  it  is  evident  that  ere  one  has  left,  another  will 
be  formed,  and  so  a  continuous  image  will  be  presented.  Now,  if  the 
images  be  thrown  upon  the  retina  so  close  to  each  other  as  to  touch, 
while  at  the  same  'time  by  the  motion  of  the  object  they  are  caused  to 
revolve  in  a  circle,  an  appearance  resembling  a  girdle  of  flame  will 
be  produced. 

Our  ideas  of  size,  distance,  surface,  polish,  and  so  forth,  are  evidently 
the  result  of  comparison  between  the  ideas  derived  from  different 
senses.  Thus,  we  feel  the  surface  of  a  table,  and  acquire  a  sense  of 
smoothness,  and  at  the  same  time  we  observe  by  the  eye  that  the  sur- 
face reflects  light  well ;  we  therefore  form  a  notion  of  polish.  In  this 
instance  we  associate  the  two  results,  and  ever  afterwards  the  notion 
of  one  recalls  the  idea  of  the  other,  and  when  we  see  anything  which 
reflects  light  well,  we  assume  that  its  surface  is  smooth  and  polished. 
The  same  statement  may  be  made  concerning  size  and  distance,  as 
the  reader  will  doubtless  admit.  The  following  remarks  on  this 
subject  are  of  great  interest : — 

"  A  boy  of  four  years  old,  upon  whom  the  operation  for  congenital 
cataract  had  beenvery  successfully  performed,  continued  to  find  his  way 
about  his  father's  house,  rather  ^feeling  with  his  hands,  as  he  haa 
been  formerly  accustomed  to,  than  by  his  newly-acquired  sense  of  sight ; 
being  evidently  perplexed  rather  than  assisted  by  the  sensation  whicn 
he  derived  through  this.  But  when  learning  a  new  locality  he  em- 
ployed his  sight,  and  evidently  perceived  the  increase  of  facility  which 
he  derived  from  it.  Among  the  many  interesting  particulars  recorded 
of  the  youth  upon  whom  Cheselden  operated  with  equal  success,  it 
is  mentioned  that,  although  perfectly  familiar  with  a  dog  and  a  cat  by 
feeling  them,  and  quite  able  to  distinguish  between  them  by  his  sight, 
it  was  long  before  he  associated  his  visual  with  his  tactile  sensations, 
so  as  to  be  able  to  name  either  animal  by  sight  alone.  The  question 
was  put  by  Locke,  whether  a  person  bora  blind,  who  was  able  by  his 
touch  to  distinguish  a  cube  from  a  sphere,  would,  on  suddenly 
obtaining  his  sight,  be  able  to  recognize  each  by  the  latter  sense.  The 
reply  was  given  in  the  negative ;  and  the  experience  of  the  cases  just 
referred  to.  as  well  as  of  many  others,  fully  justifies  such  an  answer."* 

From  what  has  been  already  observed,  we  are  justified  in  com- 
paring the  human  eye  to  the  camera  obscura  of  an  artist,  and  the 
retina  to  the  sensitised  plate  which  receives  the  image  that  is,  as  it 
were,  "developed"  by  the  influence  of  the  mind.  How  perfect  an 
apparatus  it  seems  when  we  reflect  on  the  fact  that  the  pictures 
which  it  photographs  represent  often  areas  of  square  miles,  and  are 
only  to  be  numbered  by  billions  ! 

*  Manual  of  Physiology,  byW.  B.  Carpenter,  M.D.,  F.K.S.,  F.G.S.,  &c. 
3rd  Edition,  p.  629. 


EYELIDS— TEARS— DISEASES  OF  THE  EYE.  141 

The  eyelids  are  fleshy  membranes  stretched  over  a  framework  of 
gristle.  They  are  covered  outside  by  a  layer  of  the  skin,  and  within 
by  a  delicate  fold  of  the  exquisite  mucous  structure  which  wraps  the 
eye.  By  virtue  of  the  fleshy  tissue  which  they  contain  they  can  be 
brought  together  or  separated  at  will ;  but  we  cannot  keep  them 
apart  for  any  considerable  time ;  firstly,  because  the  muscle  fibres 
which  sustain  the  upper  ones  become  exhausted  for  a  moment,  when 
the  lids  fall ;  and  secondly,  because  the  surface  of  the  eyes  becomes 


injury.  The  source  of  this  secretion  I  shall  state  presently, 
eye-lashes  serve  a  double  purpose :  they  shade  the  eye,  constituting  a 
kind  of  Venetian  blind,  and  they  prevent  the  perspiration  of  the  fore- 
head touching  upon  the  surface  of  the  cornea,  and  producing  irri- 
tation. Of  course  this  second  office  is  in  these  climates  a  sinecure. 
Not  so,  however,  in  tropical  countries,  among  the  natives  of  which  we 
find  the  eye-lashes  and  eye-brows  fully  developed.  The  function  of 
the  eye-brows  is  almost  self-evident.  They  prevent  particles  of  dust 
and  drops  of  liquid  from  passing  beyond  their  margins. 

The  tears  are  formed  from  the  blood  in  the  same  manner  as  the  saliva 
and  other  secretions,  by  the  action  of  two  small  glands  called  lachrymal. 
In  structure  each  of  these  resembles  the  salivary  glands,  which  have 
been  described  under  the  head  of  digestion,  and  is  placed  in  the  outer 
part  of  the  bony  socket  (orbit)  of  the  eye.  It  is  somewhat  of  the  form  of 
an  almond,  and  pours  its  secretion  upon  the  eye  through  six  or  eight 
little  tubes.  As  soon  as  the  tear-fluid  has  reached  the  margin  of  the 
lids,  it  passes  from  them  over  the  surface  of  the  cornea,  till  it  reaches 
the  inner  corner  of  each  eye.  Here  it  flows  through  two  small 
openings  into  a  little  reservoir,  which  in  its  turn  communicates  with 
the  nostrils.  This  arrangement  explains  two  phenomena — the  pas- 
sage of  tears  over  the  face,  and  through  the  nose — the  first  being  due 
to  an  overflow  of  the  cistern,  the  second  to  the  connection  between 
the  inner  part  of  the  nose  and  the  orbit.  Besides  the  structure 
above  enumerated,  each  lid  is  provided  with  from  twenty  to  thirty 
little  tree-like  glands,  whose  apertures  are  placed  at  the  margins,  from 
which  issues  an  oily  secretion.  The  office  of  this  is  to  prevent  the  lids 
adhering  to  each  other,  and  also  to  form  a  temporary  gutter  for  the 
tears.  It  is  it  also  which,  when  the  lids  have  been  approximated  for 
some  time  (as  in  sleep),  develops  the  ugly  gluey  material  found 
uniting  the  lids  on  rising  in  the  morning. 

Before  closing  this  chapter,  let  me  give  very  popular  definitions  of 
two  common  forms  of  disease  of  the  eye  : — 

First,  Cataract. — In  this  disease  the  crystalline  lens  becomes 
opaque,  so  that  rays  of  light  do  not  travel  through  it  sufficiently  to 
form  an  image,  it  is  cured  by  cutting  open  the  cornea,  and  ex- 
tracting the  lens. 

Second,  Amaurosis. — In  this  disease  the  retina  loses  its  power  of 
transmitting  to  the  mind  the  images  which  are  formed  on  it :  it  is,  in 
fact,  paralysed,  and  cannot  be  cured  by  any  surgical  operation,  though 
the  other  structures  are  perfect. 


142 


POPULAR  PHYSIOLOGY. 


CHAPTER  XV. 

The  Nose — Perfumes — Power  of  Scent — The  Tongue — Lingual  Papillae — 
Taste— The  Ear— Sense  of  Hearing— Nature  of  Sound— Touch. 

THE  sense  of  smell  is  seated  in  the  nostrils  (abed  e,  fig.  80),  and 
these  are  certain  cavities  contained  in  that  organ  familiarly  known 
as  the  Nose.  The  nose  is  a  kind  of  irregularly-shaped  box  with 
four  openings— two  outer  ones  above  the  upper  lip,  and  two  inner, 
placed  in  the  expansion  of  the  gullet,  called  pharynx.  It  is,  then,  one 


Fig.80. —  a  b  c  d  r  s,  membrane  of  nostrils  ;  e,  wing  of  nose  ;  n,  nose  ;  q,  nose- 
bones  ;  o,  upper  lip;  g,  jaw-bone  ;  h,  hard  palate  ;  m,  bone  of  skull;  k,  olfactory 
bulb  ;  p,  branches  of  the  latter. 

of  the  channels  through  which  air  passes  to  and  from  the  lungs,  and 
when  the  mouth  is  closed,  respiration  may  be  satisfactorily  carried 
on  with  the  assistance  of  the  nostrils. 

The  nose  is  divided  within  by  a  vertical  partition  into  two  distinct 
compartments,  and  each  of  these  is  further  divided  (partially)  by 
transverse  walls  of  bony  tissue  which  spring  from  its  sides.  The 


THE  NOSTRILS — SMELL.  143 

entire  surface  of  these  osseous  walls  is  clothed  by  a  soft,  velvety 
mucous  membrane,  bountifully  supplied  with  blood-vessels,  and 
having  numerous  small  glands  embedded  in  its  substance.  To  it  are 
also  supplied  hosts  of  filaments  of  nervous  tissue,  which  stream  down 
from  the  "  olfactory  bulbs,"  *  and  are  the  organs  through  which  the 
impressions  of  odours  are  conveyed  to  the  cerebrum.  There  are  other 
nerves  which  are  distributed  to  the  nasal  membrane,  conferring  upon 
it  common  sensibility,  the  power  of  secreting  mucus,  etc.,  which  we 
shall  not  consider  in  so  general  a  review  of  the  apparatus  as  the 
present.  The  nostril  being  placed  as  a  sentinel  upon  the  entrance  to 
the  lungs,  and  having  the  power  of  examining  everything  which  is 
about  to  enter  in  the  gaseous  form,  necessarily  constitutes  a  very  im- 
portant means  of  protecting  these  organs  from  injuries  to  which  they 
would  otherwise  be  constantly  liable.  For  example,  pure  air,  in 
traversing  the  nose-passages,  produces  no 'unpleasant  effect:  but  let 
it  be  adulterated  to  a  small  extent  with  a  foul  vapour,  such  as  sul- 
phuretted hydrogen,  and  the  result  is,  that  the  noxious  gas  being 
perceived  by  the  sensitive  membrane  of  the  nostrils,  a  conception  of 
danger  is  formed  in  the  mind,  we  immediately  refuse  to  expire  such 
an  atmosphere,  and  rushing  from  ic  in  a  state  of  intense  alarm,  seek 
fresher  and  purer  air  in  some  other  locality.  The  nose  is,  therefore, 
in  some  measure,  the  guard-house  of  the  lungs. 

That  it  is  of  use  as  a  special  organ  by  which  we  have  the 
power  of  gratifying  our  sensual  desires,  is  evident  to  those  who  love 
the  perfume  of  flowers.  It  also  serves  another,  and  more  utilitarian 
purpose,  though  rather  in  the  lower  animals  than  in  man, — the  power 
of  recognizing  certain  races  by  the  odours  which  emanate  from  them. 
Through  this  faculty  the  beasts  of  prey  are  enabled  to  "  scent "  their 
food,  and  the  Peruvian  and  other  Indians  can  distinguish  between 
various  tribes,  even  though  the  sense  of  sight  be  absent. 

Just  as  the  eye  becomes  dead  to  a  certain  colour  when  it  has  been 
gazing  on  it  for  some  time,  so  may  the  nose  become  insensible  to  any 
odour  to  which  it  has  been  long  exposed :  thus  surgeons,  anatomists, 
and  apothecaries  become  accustomed  to  the  (to  others)  very  unplea- 
sant smells  by  which  they  are  surrounded,  so  that  after  a  while  they 
do  not  perceive  them.  The  likes  and  dislikes  of  persons  relative 
to  odours  are  very  remarkable  :  to  one  the  smell  of  asafotida  is 
delicious,  to  others  disgusting.  Some  hysterical  women  are  delighted 
by  the  smell  of  burnt  feathers,  an  aroma  which  is  productive  of 
vomiting  in  those  who  enjoy  good  health.  Substances  alone  which 
give  off  a  part  of  their  component  atoms  in  the  form  of  vapour,  are 
recognized  by  the  nose.  From  this  we  conclude  that  the  sensation 
produced  in  the  nostrilsf  is  due  to  the  lodgment  of  an  infinitesimally 
minute  particle  in  the  mucous  membrane  of  the  nose.  That  an  exceed- 
ingly small  particle  is  sufficient,  has  been  shown  by  experiment.  If 

*  Two  root-like  grey  projections,  which  originate  in  the  front  portion 
of  the  brain,  and  from  their  position  on  the  base  of  the  skull  above  the 
nose,  send  down  clusters  of  fibres  to  the  membrane  of  the  nostrils. 

t  Or  rather  referred  to  the  nostrils. 


144  POPULAR  PHYSIOLOGY. 

we  make  with  spirit  an  extract  of  one  grain  of  musk,  and  add  to  it 
thirteen  million  times  as  much  water  as  there  was  of  musk,  then 
each  of  these  thirteen  million  measures  of  water  will  contain  the  one- 
thirteen-millionth  of  a  grain  of  the  odorous  substance.  And  as  each 
of  these  measures  has  a  distinct  perfume,  it  is  evident  that  we  can 
detect  the  one-thirteen-millionth  of  a  grain  of  musk  by  the  aid  of 
the  nostrils. 

A  grain  of  musk  which  had  been  exposed  in  a  room  for  ten 
years,  and  which  >  during  that  period  had  given  a  perceptible 
perfume  to  everything  in  its  vicinity,  was  found  afterwards  to  have 
lost  no  weight  appreciable  by  the  most  accurate  balance.  In  smelling 
it  is  necessary  that  the  mucous  membrane  be  moist,  for  it  has  been 
found  that  when  the  nerve  which  endows  the  nostrils  with  the  power 
to  secrete  fluid  is  cut,  the  sense  of  smell  is  lost;  and  furthermore, 
that  when  glycerine  is  rubbed  over  the  surface  with  a  feather  the 
sense  is  regained.  If  there  be  an  excessive  secretion  of  moisture,  as 
in  influenza,  the  power  of  perceiving  odours  by  the  nose  does  not 
exist. 

It  is  yet  a  question,  whether  the  "  olfactory  "  sense  is  resident 
in  the  so-called  olfactory  bulbs,  and  a  very  interesting  case,  bearing 
upon  the  question,  has  been  recorded  by  a  learned  French  physiolo- 
gist. When  dissecting  the  head  of  a  female  subject  he  found  that  both 
"  olfactory  lobes "  and  the  nerves  of  smell  were  absent,  and  could 
never  have  been  present.  This  led  him  to  make  inquiries  among  the 
friends  of  the  deceased,  the  result  of  which  was  a  general  statement  on 
their  parts,  to  the  effect,  that  when  living  the  woman's  sense  of  smell 
had  been  very  perfect,  and  that  pleasant  and  unpleasant  odours 
affected  her  as  they  did  other  persons ;  thus  proving  that  without 
what  are  thought  to  be  the  essential  portions  of  this  sense-organ  the 
woman  enjoyed  the  faculty  nevertheless. 

Organ  of  Taste. — The  faculty  of  taste  lies  in  the  Tongue,  whose 
function  is  a  threefold  one,— 

1st.  It  assists  in  swallowing. 

2nd.  Speech  is  in  great  part  effected  by  it. 

3rd.  Taste  or  gustativeness  is  seated  in  it. 

Look  down  upon  the  upper  surface  of  the  human  tongue  (fig.  81), 
and  you  will  perceive  a  great  number  of  little  elevations,  which 
anatomists  call  papilla.  Besides  those  which  you  see  there  are 
many  others,  which  are  concealed  from  your  view.  There  are 
three  sorts  of  perceptible  papillae :  —  1st.  Conical  forms  (c), 
which  project  considerably  from  the  surface,  and  are  scattered 
here  and  there  over  the  point  and  borders  of  the  tongue. 
2nd.  Whip-like  varieties  (£),  springing  from  the  general  surface 
of  the  organ,  and  surrounding  the  conical  ones  which  lie  in  their 
midst.  3rd.  Circumvattate  (h  I),  or  ditched-round  papillae.  These,  like 
the  others,  are  projections,  but  they  have  peculiar  features  which 
distinguish  them  from  the  rest.  Each  elevation  is  surrounded  by  a 
little  trench,  which  is  fenced  in  by  an  outer  wall  of  membrane— 
they  are  miniature  towers  encompassed  by  their  moats.  The  cir- 
cumvallate  papillse  are  not,  like  the  other  sorts,  distributed  over 


THE   TONGUE. 


145 


the  surface,  but  are  confined  to  one  locality, — the  base  or  root  of 
the  tongue  (see  fig.  81).  All  the  papilla?  are  composed  of  the 
following  structures : — 

(a)  A  complex  knot  of  very  smail  blood-vessels. 

(b)  Within  the  knot  a  beautiful  leash  of  delicate  nerve-fibres, 

which  receive  the  impressions. 

(c)  A  covering  of  transparent,  almost  structureless  membrane. 

The  tongue  is  moved  by  a  complicated  machinery  of  muscles,  which 
make  up  its  substance  ;  and  having  three  properties— those  of  con- 


Fig.  81.— The  Human  Tongue. 

tractility  (motion),  common  sensibility,  and  sensibility  to  taste — it  is 
supplied,  as  we  might  have  expected,  with  nerves  from  three  different 
sources  (efg,  fig.  81).  We  found  that  the  organ  of  smell  was  only  scn- 

L 


146  POPULAR  PHYSIOLOGY. 

sible  to  substances  in  a  state  of  vapour ;  on  the  other  hand,  the  organ  of 
taste  is  only  sensible  (in  a  gustative  sense)  to  substances  in  the  liquid 
condition.  Such  materials  as  arsenic,  alumina,  etc.,  give  rise  to  no 
taste, — are  tasteless,  because  they  are  insoluble  in  the  liquids  of  the 
mouth.  We  are  accustomed  to  regard  the  tongue  as  the  exclusive 
organ  of  taste,  and  as  having  the  power  of  receiving  gustative 
impressions  at  any  point  on  its  surface.  Both  these  notions  are 
erroneous. 

Place  a  small  piece  of  salt,  or  a  bit  of  aloes,  upon  the  front  of  the 
tongue,  and  so  long  as  the  substance  does  not  pass  to  the  root,  the 
peculiar  flavour  will  not  be  detected.  The  sense  is  absent  in  the 
following  parts : — 

The  front  half  of  the  tongue  on  its  upper  surface, 

The  gums, 

The  inner  surface  of  the  cheeks, 

The  skin  of  the  hard  palate ; 

and  is  present  in  the  arch  of  the  palate  beneath  which  the  food 
passes,  the  soft  palate  audits  projection  the  uvula,  and  in  the  mem- 
brane which  attaches  the  tongue  to  the  trap-door  of  the  organs  of 
voice ;  besides  being  in  its  most  highly-developed  condition  in  the 
circumvallate  papillae  which  stud  the  surface  of  the  base  (or  root)  of 
the  tongue. 

The  sense  of  taste,  like  that  of  smell,  is  often  very  delicate.  Bitter 
and  acid  substances  are  detected  when  present  in  smaller  quantities 
than  sweets  ;  thus,  the  taste  peculiar  to  each  can  be  perceived  with 
the  one-six-thousandth  part  of  a  grain  of  oil  of  vitriol,  the  one-three- 
thousandth  of  a  grain  of  extract  of  aloes,  and  the  one-four -thousandth 
of  a  grain  of  sulphate  of  quinine. 

When  a  sick  person  complains  of  a  nauseous  taste,  it  is  probable 
that  the  altered  Iblood  has  thrown  out  a  peculiar  secretion  to  which 
the  unpleasant  flavour  is  due.  There  has  been  much  controversy  as 
to  the  exact  function  of  each  of  the  nerves  which  supply  the  tongue, 
a  great  many  conflicting  statements  have  been  made,  and  the  difficulty 
in  drawing  a  rational  deduction  is  so  considerable  that  \ve  shall  do 
well  to  leave  the  question  "  sub  judice  ;"  for  its  complexities  would 
serve  rather  to  retard  the  genera  I  readex's  progress  than  to  assist  it. 

Organ  of  Hearing. — This,  as  everybody  knows,  is  the  Ear;  but  though 
all  are  familiar  with  its  external  features,  but  few  are  aware  how  in- 
teresting an  apparatus  it  is  within.  The  ear  is  composed  of  two  parts 
and  a  connecting  channel— the  outer  ear,  inner,  and  auditory  passage 
(fig.  82).  The  external  ear  is  a  gristly,  skinny  structure,  adapted  to 
catch  the  various  vibrations  of  the  atmosphere  which  are  produced 
by  bodies  that  emit  sounds.  The  central  cavity,  or  funnel,  which  is 
continuous  with  the  passage,  is  called  the  concha  ;  and  the  other  por- 
tions are  known  to  anatomists  by  numerous  designations,  which  I 
need  not  here  allude  to. 

The  inner  mechanism  is  lodged  in  the  substance  of  one  of  the  bones 
of  the  skull,  and  is  supplied  with  a  nerve— the  auditory  (»,  fig.  82) — 
presiding  over  the  sense  of  hearing  especially.  It  does  not  com- 


ANATOMY  OF  TIIE  EAK.  147 

municate  directly  with  the  external  ear,  for,  at  the  end  of  the  passage 
is  fixed  more  or  less  tensely  a  membranous  cover,  which  is  termed  the 
tympanic  membrane — or,  more  frequently,  the  drum. 

This  tympanic  membrane  is  a  kind  of  partition  between  the  two 
divisions  of  the  organ.    It  does  not,  however,  form  the  immediately 


Fig-.  82. — Inner  and  Outer  Ear. 


outer  boundary  of  the  inner  mechanisms— a  cavity  lying  between, 
these  latter  and  the  drum  styled  the  middle  ear.  How  then  is  the 
sound-vibration  conveyed  from  the  tympanum  to  the  internal  appa- 
ratus where  the  nerve  which  is  to  receive  the  impression  lies  ?  By  an 
L  2 


148  POPULAR  PHYSIOLOGY. 

exquisitely  small  chain  of  bones.*  which  are  placed  end  to  end,  one 
of  whose  extremities  is  fitted  to  the  drum  and  the  other  attached  to 
the  true  ear.  Of  what  does  the  real  auditory  organ  consist  ?  Ot 
three  portions,  collectively  called  the  labyrinth— a  name  sufficiently 
indicative  of  their  complex  arrangement  and  character.  These  three 
portions  are — 

1st.  The  semicircular  canals. 

2nd.  The  snail-shell,  or  cochlea. 

3rd.  The  vestibule,  a  cavity  intermediately  placed. 
The  labyrinth  is  provided  with  two  apertures,  covered  during  life 
with  little  membranous  shutters.  One  is  called  the  round  (o),  and 
the  other  the  oval  opening  (/),  and  into  the  latter  is  fixed  the  broad 
end  of  the  stirrup  bone.  Under  ordinary  circumstances  this  laby- 
rinth is  filled  with  fluid,!  and  by  this  the  impressions  conveyed  by  the 
chain  of  bones  from  the  drum  to  the  oval  opening  are  carried  to  the 
different  terminations  of  the  nerves  of  hearing. 


Fig.  83.— Inner  Ear  exposed. 

The  semicircular  canals  (fig.  83  left  side)  are  three  bony  tubes,  curved 
in  a  somewhat  semicircular  manner,  and  arranged  at  right  angles  with 
each  other.  These  dilate  at  their  extremities,  and  in  the  expansions  are 

E laced  the  swollen  ends  of  branches  of  the  nerve  of  hearing.    The 
inction  of  these  peculiar  structures  has  not  yet  been  ascertained 
with  certainty,  but  from  what  is  known  of  them  it  seems  not  unlikely 
that  it  is  through  them  that  we  are  enabled  to  judge  of  the  locality 
from  which  a  sound  has  travelled. 

*  These  on  account  of  their  shape  have  been  named  (from  without 
inwards)  the  hammer  (d),  the  anvil  (e),  and  the  stirrup  (/).  (See  fig.  82.) 

f  It  is  yet  to  be  proved  that  there  is  no  fluid  in  the  snail-shell  or 
cochlea. 


HOW  WE   HEAR  SOUNDS.  14:9 

The  snail-shell  or  cochlea  (fig.  S3,  right  side)  has  an  outline  which  its 
name  hints  at.  It  is  a  canal  coiled  round  a  central  axis  for  two  and  a 
half  turns,  and  it  communicates  with  the  vestibule — which  is  simply  the 
space  intervening  between  this  structure  and  the  canal— by  an  aperture. 
Its  spiral  cavity  is  divided  by  a  partition  into  two  channels,  and  on 
this  partition  is  placed  a  beautifully  toothed  membrane,  whose  office 
is  not  well  understood.  The  tube  composing  the  cochlea  expands 
into  a  dome-shaped  chamber  at  the  top  of  the  spire,  and  has  supplied 
to  it  an  extensive  branch  of  the  auditory  nerve.  From  several  obser- 
vations regarding  the  development  of  this  mechanism,  and  the  powers 
of  animals  to  appreciate  the  pitch  of  sound-impressions,  it  has  been 
concluded  as  probable,  that  its  use  is  to  enable  us  to  acquire  an  idea 
of  the  pitch  (or  length  of  the  scale)  of  different  sounds. 

You  may  perhaps  ask  what  is  the  middle  ear  filled  with  ?  It  con- 
tains only  air.  But  how  comes  air  in  such  a  position  ?  By  a  very 
beautiful  contrivance.  There  is  a  half-bony,  half-membranous  canal* 
(b,  fig.  82)  which  passes  downwards  from  _  the  cavity,  and  opens 
into  the  back  part  of  the  throat,  and  which  in  health  allows  the 
air  to  travel  upwards  or  downwards,  according  to  circumstances. 
If  the  air  in  the  middle  ear  expanded,  it  would  (had  it  no  means  of 
egress)  cause  the  drum  to  bulge  out,  and  so  would  seriously  interfere 
witli  tne  reception  of  sounds.  Of  this  the  reader  may  convince  him- 
self by  closing  the  mouth  and  nostrils  and  attempting  to  breath  out ; 
he  will  then  feel  the  drum  pushed  gradually  outwards, — an  intense 
singing  in  the  ear  accompanying  this  alteration.  The  connection 
through  this  canal  of  the  middle  ear  and  throat  explains  how  it  is 
that  an  attack  of  cold  in  the  latter  affects  the  ear  also,  giving  rise  to 
a  sensation  of  " dinning"  and  to  partial  deafness. 

Having  examined  the  three  divisions  of  the  ear,  we  can  now  under- 
take the  consideration  of  the  way  in  which  the  sounds  (or  rather  the 
vibrations  ;  for  sound  is  the  name  of  an  idea)  are  propagated  from 
the  drum  to  the  terminations  of  the  nerve  of  sense. 

Glance  at  fig.  82,  and  on  it  map  out  the  route  of  the  vibrations. 
I  strike  the  string  of  a  violin  and  instantly  it  is  thrown  into  a 
flutter,  moving  from  side  to  side  in  such  a  rapid  manner  that 
the  movements  are  hardly  perceptible  ;  at  the  same  time  a  sensation 
of  sound  is  communicated  to  the  mind.  How  does  all  this  take 
place  ?  When  the  string  was  touched,  owing  to  its  tenseness,  it  com- 
menced a  series  of  vibrations— of  imperceptible  movements  from  side 
to  side— striking  the  air  in  its  vicinity.  By  this  the  more  distant  air 
was  caused  to  move,  until  at  length  that  portion  of  the  atmosphere 
in  the  neighbourhood  of  the  ear  was  affected,  and  finally  the  drum  of 
the  ear  itself.  The  column  of  air  which  was  thus  caused  to  undu- 
late is  called  a  wave ;  the  wave  began  at  the  violin  string,  and  tra- 
velled onward  at  the  rate  of  about  1,125  feet  in  the  second,  till  it 
ended  at  the  drum  or  membrane,  from  which  we  shall  now  trace  its 
progress  inwards. 

The  drum  having  received  the  vibration  which  has,  so  to  speak, 

*  The  Eustachian  tube. 


150  POPULAR  PHYSIOLOGY. 

traversed  the  auditory  channel  (a],  transmits  it  to  the  hammer-bone 
(d)  ;  this  gives  it  to  the  anvil  (e],  from  which  it  is  forwarded  to  the 
stirrup  (/),  and  at  length  arrives  at  the  oval  opening  of  the  internal 
ear.  Arrived  here,  it  (the  vibration)  is  communicated  to  the  fluid 
which  pervades  the  labyrinth,  and  is  possibly  conveyed  in  part 
through  the  semicircular  canals  and  the  snail-shell  (fig.  S3).  In  Both 
of  these  organs  it  strikes  against  the  recipient  terminations  of  the 
nerve— in  the  first  it  gives  rise  to  a  notion  *  not  only  of  sound,  but 
also  of  the  direction  in  which  the  sound  travelled  (?) ;  whilst  in  the 
second  an  impression  is  produced  which  gives  an  idea  of  the  pitch  of 
the  sound  emitted  by  the  string.  I  said  that  the  vibrations  into  which 
the  string  was  thrown  were  communicated  to  the  air,  and  from  it  to 
the  ear-drum ;  from  which  you  will  draw  the  inference  that  if  there 
was  no  air  no  sound  would  be  heard ;  and  this  is  really  the  case. 

I  place  a  bell  in  the  upper  portion  of  a  glass  shade  in  such  a 
position  that  when  the  shacfe  is  moved  the  bell  will  be  caused  to 
sound ;  if  now  I  move  the  shade  you  will  hear  the  sound  of  the 
bell  distinctly.  ^  In  the  next  instance  I  fix  the  shade  over  an  air- 
pump,  and  having  worked  the  instrument  for  a  few  moments,  then 
ring  the  bell,  and  mark  at  once  that  the  sound  is  fainter  than  before. 
I  continue  to  work  at  the  pump  till  I  have  thoroughly  exhausted  the 
air ;  now  I  again  ring  the  bell,  but  though  I  can  distinctly  perceive 
the  tongue  striking  against  the  sides,  the  bell  is  dumb,  the  sound  is 
no  longer  distinguished.  I  again  admit  the  air,  and  all  goes  on  as 
before. 

From  the  above  experiment  you  are  led  to  believe  that  the  air 
conducts  the  vibrations  to  our  ears,  but  you  must  not  conclude  that 
in  air  alone  resides  the  power ;  wood,  iron,  and  water  can  also  con- 
vey sound  very  perfectly.  The  newest  form  of  stethoscopef  is  com- 
posed of  a  solid  rod  of  whalebone  or  cane,  and  the  sounds  of  the 
heart  can  be  detected  quite  as  distinctly  with  it^  as  with  the  older 
form  of  the  instrument.  The  latter  was  hollow  in  the  interior,  and 
impressed  the  patient  with  such  an  idea  of  fire-arms,  that  it  was  a 
very  formidable  weapon  in  the  hands  of  those  physicians  who,  not 
possessed  of  much  originality  of  their  own,  delighted  to  ape  the 
Abernethy. 

The  physiology  of  the  organ  of  hearing  is  even  yet  involved  in  so 
much  uncertainty,  that  to  enter  upon  loose  and  unscientific  explana- 
tions of  well-known  phenomena  would  do  no  service  to  the  reader, 
who  (if  he  has  carefully  perused  the  foregoing  paragraphs)  will  be 
in  possession  of  as  much  information  upon  the  subject  as,  for 
the  present,  he  can  hope  to  obtain. 

Our  ideas  of  the  distance  of  sound  are  derived  from  the  intensity 
of  the  vibrations,  and  from  habit.  That  this  is  true  is  evident  from 
the  fact,  that  if  a  sound  be  produced  near  us,  but  yet  of  the  same 
intensity  as  it  would  have  had  had  it  come  from  a  distance,  we  will 

*  Co-operating,  of  course,  with  the  brain  and  mind, 
•j-  The  credit  of  this  discovery  is,  I  believe,  due  to  Dr.  Corrigan,  of 
Dublin. 


CONDUCTION  OF  SOUND — TOUCH.  151 

be  deceived  as  to  the  locality  from  which  it  emanates.  This,  in  fact, 
is  what  is  done  by  all  those  who  possess  the  power  of  ventrilo- 
quising. 

It  is  stated  that  sounds  of  a  very  small  number  of  vibrations  per 
second  (14  to  16),  are  unappreciated  by  the  human  ear,  and  that 
those  which  are  composed  of  more  than  64000  in  the  second  are 
also  imperceptible.  It  is,  however,  quite  sufficient  to  excite  our 
wonder  to  know,  not  only  that  notes  within  these  far  distant  limits 
are  cognizable  distinctly,  but  that  during  a  single  second  a  string 
may  be  caused  to  vibrate  sixty-four  thousand  times. 

The  faculty  of  hearing  may  be  developed  in  different  directions : 
one  man  may  possess  great  acuteness  as  regards  the  perception  of 
sounds  generally,  another  as  regards  the  perception  of  musical 
sounds,  and  so  on ;  but  it  is  unquestionable  that  the  auditory  sense 
may  be  much  increased  by  cultivation.  To  quote  the  language  of 
one  of  the  most  philosophic  writers  in  the  English  scientific  world : 
"  The  watchful  North  American  Indian  recognizes  footsteps,  and 
can  even  distinguish  between  the  tread  of  friends  and  foes ;  whilst 
his  white  companion  who  has  lived  among  the  busy  hum  of  cities 
is  unconscious  of  the  slightest  sound.  Yet  the  latter  may  be  a 
musician  capable  of  distinguishing  the  tones  of  all  the  different 
instruments  of  a  large  orchestra,  of  following  any  one  of  "them  through 
the  part  which  it  performs,  and  of  detecting  the  least  discord  in  the 
blended  effects  of  the  whole— effects  which  would  be,  to  the  unso- 
phisticated Indian,  but  an  indistinct  mass  of  sound.  In  the  same 
manner,  a  person  who  has  lived  much  in  the  country  is  able  to  dis- 
tinguish the  note  of  every  species  of  bird  that  lends  its  voice  to  the 
general  chorus  of  nature ;  whilst  the  inhabitant  of  a  town  hears 
only  a  confused  assemblage  of  shrill  sounds,  which  may  impart  to 
him  a  disagreeable  rather  than  a  pleasurable  sensation."  < 

Sense  oj  Touch. — When  we  bring  the  ends  of  our  fingers  into  contact 
with  any  object,  an  impression  is  immediately  produced  upon  the  sur- 
face of  the  skin,  which  is  applied  to  the  object,  and  this  impression 
being  conveyed  by  the  sensitive  nerves  to  the  spinal  chord  and  brain, 
an  idea  concerning,  the  surface  of  the  thing  felt  is  forthwith  formed 
by  the  mind.  We  say  we  have  felt  it.  It  is  soft  or  hard,  or  smooth  or 
rough  according  to  circumstances.  The  power  which  we  thus  possess 
of  conceiving  of  the  nature  of  surface,  without  the  aid  of  the  eye, 
is  called  the  faculty  of  touch.  The  faculty  is  seated  in  the  skin 
generally,  but  particularly  in  the  skin  of  the  fingers.  It  is  not,  how- 
ever possessed  by  the  skin,  but  by  certain  structures  in  it,  which 
communicate  with  the  terminations  of  the  truly  sensitive  nerves.  To 
be  plain,  it  resides  in  the  extremities  of  these  nerves. 

How  do  we  prove  that  the  sense  is  resident  in  the  nerves  ?  Easily 
enough.  We  walk  into  one  of  the  wards  of  a  hospital,  and  sitting  beside 
the  bed  of  a  patient  who  is  suffering  from  such  a  disease  of  the  spinal 
chord  that  the  latter  is  virtually  amputated,  we  with  a  feather  tickle  the 
soles  of  his  feet.  This  produces  an  exceedingly  unpleasant  sensation 
in  a  healthy  man,  but  in  the  present  case  it  is  unfelt.  Nextly,  we  place 
our  hands  upon  his  limbs,  and  he  tell  us  that  he  does  not  feel  them, 


152 


POrULAll  PHYSIOLOGY 


Fig.  84. 


and  that  had  he  not  seen  their  position  he  would  not  have  believed 
that  they  were  in  contact  with  him.    Why  is  the  sense  absent  here  ? 

Because  the  spinal  chord 
being  divided,  the  line  of 
communication  between  the 
surface  of  the  limbs  and  the 
brain  is  severed — the  tele- 
graphic wire  has  been  cut, 
and  the  messages  to  the 
mind  are  no  longer  trans- 
mitted. When  a  portion  of 
the  skin  of  the  finger  (cut  at 
right  angles  to  the  surface) 
is  placed  in  the  field  of  the 
microscope,  the  observer 
may  perceive  beneath  the 
outer  or  scarf-skin,  a  vast 
number  of  little  teat-like 
elevations,  called  papilla; 
(fig.  84).  To  each  of  these 
passes  a  small. blood-vessel,  and  also  a  minute  twig  from  the  sensitive 
nerve:  the  first  forms  a  few  loops  round  the  papilla?;  the  second 
enters  its  substance. 

Anatomists  have  also  discovered  a  microscopic  body  in  the  interior 
of  many  of  these  papilla?.  It  is  in  form  like  a  fir- 
cone, and  according  to  some  is  hollow  in  the 
interior— to  others,  is  a  solid  structure.  At  this 
body  the  filament  of  the  sensitive  nerve  ends, 
either  by  entering  its  substance  and  passing 
through  its  centre,  or  by  winding  round  it  in  a 
spiral  manner  (b  c  d  e,  fig.  85). 

As  these  little  organs  have  not  been  invariably 
found  co-existing  with  the  tactile  sense,  it  follows 
that  they  are  not  essential  to  it.  That  they  may 
nevertheless  intensify  the  faculty  of  touch  when 
they  are  present,  seems,  as  has  been  suggested, 
not  unlikely. 

The  number  of  the  elevations  I  have  described 
is  indeed  astounding ;  they  (papillse)  are  placed  in 
double  rows,  containing  about  sixty  each;  and  ^as 
there  are  no  less  than  forty  of  these  bi-linear  series 
in  the  square  inch,  it  results  that  within  this  small 
space  there  are  no  less  than  two  thousand  four 
hundred  distinct  points,  each  capable  of  receiving 
some  impression  from  an  external  object.  This 
statement  is  true  only  for  the  skin  of  the  fingers, 
where  the  elevations  are  most  abundant;  in 
other  localities  the  papilla?  are  much  more 
Fig.  85.— A  Pacinian  sparingly  distributed.  For  this  reason,  the 
Corpuscle.  sense  of  touch  is  more  highly  developed  in  the 


THE  TACTILE   SEXSE.  153 

hand  than  in  other  portions  of  the  body.  A  German  physiologist 
proved  this  very  ingeniously.  He  took  a  pair  of  compasses,  and 
having  brought  the  legs  close  to  each  other,  he  placed  them 
in  contact  with  the  skin  of  the  hand,  and  found  that  a  sensation 
was  produced,  such  as  would  have  resulted  from  the  application  of 
two  different  objects  ;  from  this  he  concluded  that  the  two  points 
were  brought  into  contact  with  two  distinct  papillae.  Next,  he 
touched  a  portion  of  the  skin  of  the  back  (keeping  the  legs  of  the 
instrument  at  the  same  distance  from  each  other  as  before),  and  dis- 
covered that  but  one  point  was  perceived,  because  there  were  not 
two  sensitive  elevations  sufficiently  close  to  be  in  contact  with  both 
ends  of  the  compass.  He  now  increased  the  distance  between  the 
legs,  and  on  again  applying  it  to  the  skin,  remarked  that  both  points 
were  perceived.  By  an  extensive  series  of  experiments  of  this  de- 
scription, he  was  enabled  to  arrive  at  the  following  conclusions  :  — 

That  the  two  points  can  be  per-  ("When  only  half  a  line  apart,  by 
ceived  and  distinguished         \     the  point  of  the  tongue. 

„  „  S  When  about  five  lines  apart,  by 

}     the  skin  of  the  finger. 
When  fourteen  lines  apart,  by 
the  skin  of  the  back  of  the 
hand. 


„  „  5  "VThen  thirty  lines  apart,  by 

I     the  skin  of  the  back. 

The  skin  may  be  regarded  as  possessed  of  two  senses,  —  one  which 
enables  us  to  form  an  idea  of  the  shape  and  surface  of  objects,  the 
other,  which  is  perhaps  an  intensified  condition  of  the  first,  which 
gives  rise  to  a  conception  of  pain.  The  latter  is  common  to  the 
flesh  and  skin,  but  the  former  belongs  solely  to  the  surface  of  the 
integunient. 

Besides  these  properties  of  the  tactile  papilla,  the  skin  enables  us 
to  form  an  estimate  of  temperature.  This  estimate,  however,  is  in 
great  part  a  relative  one,  and  depends  upon  the  actual  heat  of  the 
skin  or  part  of  the  skin  applied  to  the  object.  If  we  dip  the  hand 
into  water  at  104°  and  afterwards  into  a  fluid  at  89°,  the  latter  will 
appear  cold  ;  but  if  the  hand  be  first  placed  in  water  at  68°,  then 
that  at  89°  will  appear  to  be  lukewarm.  A  person  may  dij)  his  hand 
into  a  crucible  of  molten  lead,  and  if  it  be  allowed  to  remain  for  but 
a  moment  no  injury  will  be  sustained.  This  is  because  a  cloak  of 
vapour  is  formed  round  the  surface  of  the  hand,  owing  to  the  evapo- 
ration of  the  fluids  of  the  skin,  and  this  layer  of  moisture  protects 
the  hand  from  being  burnt.  Lecturers  on  physics  are  accustomed  to 
perform  an  experiment  whose  principle  is  the  same.  They  make  a 
platinum  spoon  red-hot,  and  pour  a  drop  of  water  into  it  ;  the  water 
is  not  boiled,  but  assumes  a  spherical  form,  and  remains  upon  the 
spoon.  This  is  because,  at  the  moment  it  was  placed  upon  the  red- 
hot  surface,  the  outer  layer  of  the  fluid  was  converted  into  vapour, 


154  POPULAR  PHYSIOLOGY. 

which  enveloped  the  globule,  and  prevented  the  action  of  the  sur- 
rounding temperature  upon  it. 

It  is  strange  that  when  a  large  surface  of  the  skin  is  exposed  to  the 
influence  of  warm  or  cold  water,  the  fluid  appears  of  a  higher  or 
lower  temperature  than  if  a  small  portion,  as  the  finger  for  example, 
were  dipped  into  it. 

Pain,  such  as  that  experienced  in  case  of  burns,  can  only  be  produced 
by  substances  whose  temperature  is  less  than  50°,  or  over  122°. 

Our  conceptions  of  weight  are  in  some  measure  dependent 
upon  the  portion  of  the  skin  to  which  the  bodies  are  applied ; 
thus,  if  a  billiard-ball  be  allowed  to  roll  down  the  face,  from  the 
cheek-bone  to  the  lips,  it  will  appear  to  increase  in  weight  as  it 
approaches  the  latter,  because  the  sense  of  touch  is  more  highly 
developed  in  this  locality  than  in  the  upper  portions  of  the  face.  In 
all  cases  of  the  measurement  of  weight  by  the  hands,  we  are  likely 
to  be  deceived,  unless  we  bring  in  the  other  senses  to  our  aid. 
For  instance,  we  see  the  object,  and  from  its  size  form  a  vague 
notion  of  its  heaviness.  Then  by  touch  we  know  whether  it  be  porous 
or  dense,  a  good  conductor  of  heat  or  not,  and  we  draw  very  impor- 
tant conclusions  from  these  observations.  Finally,  we  lift  it,  and  by  a 
mental  comparison  between  the  amount  of  muscular  exertion  required 
to  raise  it,  and  necessary  for  the  elevation  of  some  9ther  body  whose 
weight  is  known,  we  decide  how.  heavy  it  is.  Habit  and  experience 
have  much  to  do  with  the  development  of  this  sense.  We  fancy 
when  blindfold  that  the  same  body  placed  in  each  hand  is  heavier 
in  the  left  than  in  the  right.  Preconceived  ideas  influence  our 
decisions  to  a  great  extent. 

When  Sir  H.  Davy  discovered  the  metal  potassium,  which  is  so  light 
that  it  will  float  on  water,  and  placed  it  in  the  hands  of  a  friend,  the 
latter  remarked,  "Bless  me,  how  heavy  it  is." 

I  bandage  your  eyes,  and  taking  your  fore-finger  in  my  hands,  I  place 
it  on  the  table,  and  press  it  against  the  surface,  first  lightly,  then  more 
heavily,  and  you  exclaim,  "  You  are  moving  my  finger  over  some  glo- 
bular body."  I  reverse  the  order  of  pressure,  and  you  say,  "  My  finger 
now  passes  over  some  hollow  substance."  The  correcting  sense  (sight) 
is  absent,  and  the  organ  of  touch  being  excited  in  the  same  manner  as 
it  would  have  been  in  passing  over  a  convex  and  concave  surface,  you 
really  conceived  that  in  each  case  the  plain  surface  of  the  table  had 
one  of  these  two  characters.  The  tactile  sense  is  usually  more  perfect 
among  the  blind  than  in  ordinary  individuals.  It  has  been  said  of  a 
celebrated  Cambridge  professor  that,  though  blind,  he  could  with 
the  utmost  facility  distinguish  between  genuine  and  spurious  medals 
by  the  sense  of  touch  alone ;  and  instances  have  been  recorded  of 
blind  men  who  possessed  the  faculty  of  discriminating  by  touch 
alone  between  textures  of  different  colours.  In  order  to  show  the 
deceptive  character  of  the  sensations  arising  from  tactile  impressions, 
schoolboys  perform  the  following  experiment : — Cross  the  fore  and 
middle  fingers  of  a  person  whose  eyes  are  closed,  and  place  a  marble  in 
such  a  position  that  it  touches  the  extremities  of  both  fingers.  The  person 
will  receive  an  impression  the  same  as  that  which  icould  have  resulted 


CONCEPTIONS   OF  WEIGHT  AND  FORM. 


155 


from  the  actual  contact  of  two  marbles  (fig.  86).  What  is  the  cause 
of  this  deception  ?  When  the  marble  is  placed  simply  between 
two  fingers  there  is  no  deceptive  impression,  because  these  are  felt 
by  the  surfaces  of  the  skin,  one  convex  outwards  and  the  other  con- 
vex inwards ;  and  these  two  we  unite  oy  one  judgment  to  the  con- 
ception of  a  solid  ball.  In  the  exceptional  and  deceptive  instance, 
the  two  convex  surfaces  appear  (on  account  of  our  habitual  con- 
ceptions) to  be  both  in  the  same  direction,  and  we  form  the  idea  that 
two  little  spheres  are  present.  This  is  the 
usual  explanation,  and  we  take  it,  as  people  say, 
"  with  a  grain  of  salt."  I  do  not  commit  my- 
self to  it,  merely  regarding  it  as  an  agreeable 
solution  of  the  difficulty  till  some  better  one 
turns  up. 

If  I  were  to  pile  up  experiments  and  observa- 
tions of  the  kind  I  have  just  glanced  at,  I  should 
soon  have  a  "monster  pyramid"  indeed— a 
huge  curiosity  shop  of  ill-ascertained  facts, 
useless  statements,  and  miraculous  phenomena, 
equally  puzzling  to  the  reader  and  myself.  But 
why  inflict  upon  S9ciety  a  host  of  threadbare 
anecdotes  about  this  man,  and  that,  and  the 
other  ?  Enumerate  phenomena  bordering  upon 
the  marvellous— cm  bono?  Let  the  accumu- 
lation I  have  exhibited  suffice,  and  should  the 
reader  desire,  let  him  peruse  the  works  of  those 
modem  writers  who  revel  in  anecdotes,  and  love  to  Indulge  the  public 
with  sensation  science,  for  statements  and  explanations  of  a  more 
exciting  character. 

It  is  customary  to  introduce  into  works  on  physiology  some 
description  of  the  development  of  the  human  body,  to  discuss  the 
question  how  from  an  almost  microscopic  germ  the  complex  organism, 
containing  muscles  and  veins,  skin  and  bone,  is  produced ;  to  retrace 
the  various  footprints  upon  that  ill-defined  intricate  path,  along 
which  the  being  has  journeyed  to  its  complete  from  its  immature  con- 
dition. 1  admit  that  there  are  few  points  upon  which  attention  could 
be  concentrated  with  more  interest  or  advantage ;  but,  at  the  same 
time,  I  am  fully  aware  that,  from  the  character  of  the  remarks  which 
must  necessarily  be  made  to  render  the  subject  intelligible,  and  from 
the  associations  which  the  requisite  allusions  would  call  up  in  the 
minds  of  some,  such  a  question  could  not  be  dealt  with  in  a  work  in- 
tended, as  the  present  Is,  for  the  improvement  of  the  physiologically- 
ignorant  of  both  sexes. 


Fig.  86. 


156  POPULAR  PHYSIOLOGY. 


CHAPTER     XYI. 

CONCLUSION. 

WE  have  now  arrived  at  the  terminus  of  our  physiological  railway. 
We  have  passed  slowly,  it  is  true,  along  a  lovely  country,  and  it 
behoves  us,  now  that  the  carriage  doors  are  closed,  and  we  are  seated 
in  our  homes,  to  review  mentally  the  ground  over  which  we  have 
travelled.  It  is  to  be  hoped  that  we  have  not  undertaken  the  journey 
in  the  spirit  of  mere  conventionality,  that  we  have  not  been  conveyed 
along  the  line  with  closed  eyes,  and  that  our  final  object  has  not  been 
the  wish  to  be  able  to  say^e  have  been  to  science-land.  If  we  would 
travel  for  the  sake  of  having  to  say  we  have  travelled,  we  should  recall 
the  lines  of  Hood : — 

"Some  minds  improve  by  travel,  others  rather 
Eesemble  copper  wire,  or  brass,  which  gets  the  narrower  by  going  farther." 

No,  dear  reader !  I  trust  our  eyes  have  been  open  to  the  wonders 
of  the  science  we  have  so  far  devoted  ourselves  to.  We  have  not  for- 
gotten the  maxim  that  "knowledge  is  power;"  and  what  knowledge 
is  superior  to  that  which  physiology  affords  to  the  earnest,  truth- 
seeking  student?  What,  then,  is  the  fruit  of  our  labour?  How- 
have  we  been  benefited  by  the  study  we  embraced?  We  have 
learned  something  of  all  those  complicated  phenomena  which  are 
commonly  summed  together  in  the  term  Life.  It  is  not  to  be  sup- 
posed that  by  life  we  understand  a  force  of  a  special  nature  operating 
upon  living  bodies,  nor  a  combination  of  those  ordinary  forces  which 
regulate  the  action  of  inanimate  matter ;  but  rather  that  it  is  the 
operation  of  the  one  power  which  pervades  the  universe,  and  which, 
under  different  circumstances,  exhibits  itself  in  the  production  of 
different  phenomena.  We  have  observed  how  the  two  great  classes 
of  living  beings  are  mutually  dependent  upon  each  other ;  how  the 
various  processes  of  digestion,  absorption,  circulation,  and  re- 
spiration, are  merely  the  results  of  ordinary  physical  agencies,  and  that 
no  peculiar  vital  principle  need  be  invoked  to  explain  the  mode  in 
which  they  are  achieved ;  and  how  the  special  senses,  sight,  hearing, 
touch,  taste,  and  smell,  are  to  no  slight  or  trifling  extent  under  the 
control  of  the  ordinary  laws  of  physics.  We  have  surveyed,  and 
occasionally  with  scrutinizing  care,  the  minute  structure  of  what  to 
the  naked  eye  is  almost  "  without  form  and  void ;"  and  by  the 
assistance  of  the  microscope  have  brought  even  new  worlds  within 
our  ken.  Having  for  our  motto,  "  Know  thyself,"  we  have  examined 
the  most  elaborate  work  of  the  Creator,  the  highest  summit  in  the 
grand  mountain-range  of  organization — "  God's  own  image."  Assu- 
redly, the  contemplation  of  our  very  selves  has  exalted  and  expanded 
our  minds,  and  knowing,  as  we  do,  that "  the  proper  study  of  mankind 


CONCLUSION.  157 

is  man,"  we  can  each  exclaim  with  the  divine  writer,  "  0  God,  I 
am  fearfully  and  wonderfully  made." 

A  caviller  might  insinuate  that  the  views  I  have  put  forward 
are  materialistic  in  tendency.  I  cannot  think  that  materialism 
has  been  advocated,  even  where  principleist  doctrines  have  been 
objected  to.  It  is  not  because  we  endeavour  to  account  for  the 
actions  of  living  bodies  by  referring  to  the  ordinary  laws  of  physics, 
that  we  are,  therefore,  guilty  of  materialism ;  for,  so  long  as  we 
regard  the  properties  of  matter  as  having  been  originally  impressed 
upon  it  by  the  Divine  will,  so  long  must  we  regard  their  continuance 
as  dependent  upon  the  same  Almighty  fiat  which  called  matter  itself 
into  existence  "  in  the  beginning."  In  the  words  of  one  of  England's 
most  philosophic  bards  : — 

' '  All  are  but  parts  of  one  stupendous  whole, 
Whose  body  nature  is,  and  God  the  soul ; 
That  changed  through  all,  and  yet  in  all  the  same, 
Great  in  the  earth  as  in  th'  ethereal  frame  ; 
Warms  in  the  sun,  refreshes  in  the  breeze, 
Glows  in  the  stars,  and  blossoms  in  the  trees, 
Lives  through  all  life,  extends  through  all  extent, 
Spreads  undivided,  opei-ates  unspent, 
Breathes  in  our  soul,  informs  our  mortal  part, 
As  full,  as  perfect,  in  a  hair,  as  heart ; 
As  full,  as  perfect  in  vile  man  that  mourns, 
As  the  rapt  seraph  that  adores  and  burns  : 
To  Him  no  high,  no  low,  no  great,  no  small  ; 
He  fills,  He  bounds,  connects,  and  equals  all." 


LIST  OF  WORKS, 

Which  may  lie  consulted  1y  those  who  are  desirous  of  pursuing 
the  subject  of  this  WorJc  further. 

Carpenter,  W.  B.,  M.D.,  F.R.S.— cc  Principles  of  Human  Physi- 
ology." 

"  Manual  of  Physiology." 

Dalton,  John,  M.D.,  &c.  —  "A  Treatise  on  Human  Physiology, 
designed  for  the  use  of  Students  and  Practitioners,"  with  illus- 
trations. 8vo.  Philadelphia.  1861. 

Kirkes,  Wm.  Senhouse,  M.D.,  &c.— "  Handbook  of  Physiology," 
8vo. 

Knox,  Robert,  M.D.— "  Man— His  Physiology." 

Lewes,  G.  H.— "  The  Physiology  of  Common  Life."    2  vols. 

Miiller,  Johannes. — "  Elements  of  Physiology."  Translated  by  Dr. 
Baly. 

Todd,  R.  B.,  M.D.,  and  Bowman,  Wm.,  F.R.S  — "  The  Physiological 
Anatomy  and  Physiology  of  Man."  2  vols. 

Valentin.— "A  Text-book  of  Physiology."  Translated  by  Dr. 
Brinton. 

Wagner,  Dr.  Rudolph. — "Handbook  of  Physiology." 

"The  Cyclopaedia  of  Anatomy  and  Physiology."  Edited  by 
R.  B.  Todd,  M.D,  E.R.S. 

General  Works  on  the  Microscopic  Anatomy  of  the  Body. 
Beale,  Lionel  S.,  F.R.S.—"  On  the  Structure  of  the  Simple  Tissues 
of  the  Human  Body,  with  some  Observations  on  their  Develop- 
ment and  Growth." 

Carpenter,  W.  B.,  M.D.,  E.R.S.— "  The  Microscope  and  its  Revela- 
tions." 

Gosse,  Philip  H.,  P.L.S.— "  Evenings  at  the  Microscope." 


1GO  POPULAR   PHYSIOLOGY. 

Kolliker,  Professor  Albert—"  Manual  of  Human  Histology."  Trans- 
lated by  Mr.  Busk  and  Professor  Huxley.    Syd.  Soc. 
Kolliker,  Professor  A. — "  Microscopic  Anatomy." 
Lankester,  Edwin,  P.U.S.— "  Half  Hours  with  the  Microscope." 

Quaiu,  Dr. — "  Elements  of  Anatomy."  Edited  by  "Win.  Sharpey, 
Sec.  R.S.,  and  G.  V.  Ellis,  Professor  of  Anatomy  and  Physiology 
in  University  College,  London. 

Quekett,  Thomas,  P.R.S.-"  Lectures  on  Histology." 


The  Blood. 

Harvey,  "VYm. — The  works  of,  Translated  for  the  Sydenhara  Society. 
Richardson,  B.  W. — "  Essay  on  the  Cause  of  the  Coagulation  of  the 
Blood." 


Chemistry  of  Physiology. 
Johnston,  J.  P.,  M.A. — "  Chemistry  of  Common  Life."  2  vols. 

Lehmann,  Dr. — "  Physiological  Chemistry."  Translated  by  Dr.  Day. 
Sydenham  Society. 

Liebig,  Baron. — "  Animal  Chemistry."  Translated  by  Dr.  Gregory. 
Simon,  Dr.  P. — "  Animal  Chemistry."    Translated  by  Dr.    Day. 
Sydenham  Society. 


Beaumont,  "Win.,  M.D.,  Surgeon  U'.S.  Army. — "  Experiments  and 
Observations  on  the  Gastric  Juice  and  the  Physiology  of 
Digestion." 

Beale,  L.  S.,  P.R.S. — "  On  some  Points  in  the  Anatomy  of  the  Liver 
of  Man." 

Gray,  Henry,  P.TLC.S.— "  Structure  and  Use  of  the  Spleen." 
Hassall,  A.  H.,  M.D.— "  Pood  and  its  Adulterations." 
Lankester,  Edwin,  P.R.S. — "  Twelve  Lectures  on  Pood." 


LIST  OF  WORKS.  161 

Liebig,  Baron—"  Chemistry  of  Food."  1847.  "  Researches  into 
the  Motion  of  the  Juices  of  the  Animal  Body." 

Owen,  Professor,  F.R.S.— "  Odontography." 

Prout,  Wm. — "  Chemistry,  Meteorology,  and  the  Function  of 
Digestion  considered,  with  reference  to  Natural  Theology" — 
Bridgewater  Treatise.  1834. 

Ethnology. 

Huxley,  Professor,  F.R.S.— "  Man's  Place  in  Nature." 

Knox,  R.,  M.D.— "  The  Races  of  Men." 

Lyell,  Sir  C.,  F.R.S.— "  The  Antiquity  of  Man." 

The  Eye. 

Bowman,  Wm.,  M.D.,  F.R.S. — "  Lectures  on  the  Parts  concerned  in 

the  Operations  on  the  Eye." 

Brewster,   Sir  David — "  Optics  " — Lardner's  Cyclopaedia. 
Lloyd,  Dr.— "On  Light  and  Vision." 
Mackenzie,  Wm.,  M.D. — "  Outlines  of  Ophthalmology." 
Morton,  Francis—"  Optics." 

Forces  concerned  in  Life. 

Grove, Mr.,  Q.C.,  F.R.S .— "The  Correlation  of  the  Physical  Forces." 
Matteucci,  Signor — "  Lectures  on  the  Physical  Phenomena  of  Living 
Beings." 

The  Nervous  Sy stern. 

Bain,  Alexander,  M.A.— "  The  Senses  and  the  Intellect,"  and  "  The 

Emotions  and  the  Will." 
Bell,  Sir  C.— "  Researches  in  the  Nervous  System,"  by  Alexander 

Shaw. 

Grainger,  Mr.,  F.R.C.S.— "  Observations  on  the  Spinal  Chord." 
Sequard,  Dr.  Brown,  F.R.S.—"  Lectures  on  the  Physiology  of  the 

Nervous  System." 

Solly,  Mr.,  F.KS.— "  On  the  Human  Brain." 
Todd,  R.  B.,  M.D.,  F.R.S.—"  Anatomy  of  the  Brain,  Spinal  Chord, 

and  Ganglion." 

Relation  of  Physiology  to  other  Sciences. 

Whewell,  William,  D.D.— "  History  of  the  Inductive  Sciences." 
"  Philosophy  of  the  Inductive  Sciences." 
M 


162  POPULAR  PHYSIOLOGY. 


Oil  the  Skeleton,  8fc. 

Holden,  Luther,  F.R.C.S .— "  Human  Osteology." 

Humphrey,  George,  M.D.,  E.R.S.— "  A  Treatise  on  the  Human 
Skeleton." 

Maclise,  Joseph,  P.RC.S. — "Comparative  Osteology;  being  Mor- 
phological Studies,  to  demonstrate  the  Archetype  Skeleton  of 
Yertebrated  Animals." 

Owen,    Professor,    F.R.S.,  &c.,   &c.— "  On  the    Archetype    and 

Homologies  of  the  Vertebrate  Skeleton." 

Skin. 

Wilson,  Erasmus,  E.R.C.S.— "  A  Practical  Treatise  on  Healthy 
Skin." 


INDEX. 


A. 

ABDOMEN,  11,  12. 

Abernetliy,  anecdote  of,  41. 

Aberration,  spherical  and  chromatic, 
130. 

Absorption,  44  ;  experiments  on,  42. 

Acid,  carbonic,  where  formed,  80; 
poisonous  effect  of,  81;  of  the  sto- 
mach, 35. 

Adam's  apple,  83. 

Affinity  of  air-cells  for  carbonic  acid,  59; 
tissues  for  blood,  58. 

Ague,  phenomena  of,  91. 

Air,  action  of  plants  on,  3;  cells  of 
lungs,  71;  composition  of,  80;  con- 
sumption of,  per  annum,  81 ;  mixed 
with  food  by  saliva,  33 ;  influence  of, 
on  blood,  79 ;  quantity  of,  changed  in 
lungs,  77 ;  contained  in  lungs,  77. 

Albumen  of  blood,  48 ;  egg,  23 ;  porter, 
21 ;  potatoes,  43. 

Albuminate  of  iron  and  soda,  49. 

Alcohol,  action  of,  objections  to,  20, 
21  j  production  of,  from  oxygen  and 
hydrogen,  13;  use  of,  21. 

Aloes,  smallest  particle  of,  that  can  be 
tasted,  146. 

Amaurosis,  141. 

American  physician,  views  of,  on  diges- 
tion, 45. 

Ammonia,  action  of,  on  fibrine,  48. 

Amoeba,  digestive  organs  of,  30. 

Animals  and  plants,  distinction  of,  2. 

Animal  division  of  organs  10. 

Anthropotomist,  meaning  of  the  term, 
65. 

Anvil -bone,  1 48. 

Aorta,  51,54. 

Apes,  brain  of,  11Q. 

Arborescent  form  of  lacteals,  44. 

Arm,  bones  of,  10;  mechanical  power 
of,  106,  107. 

Arsenic,  a  poison,  26. 

Arterial  and  venous  blood,  colour  of, 
49. 

Arteries,  elastic  coat  of,  50;  general, 
51  ;  pulmonary,  55. 

Asphyxia,  or  suffocation,  /O. 

Assafoatida,  action  of,  on  nose,  143. 

Association,  British,  experiments  of,  on 
circulation,  64. 

M 


Asthma,  73, 

Atropia,  action  of,  on  eye,  135. 
Auricles,   53;   and  ventricles,  commu- 
nication between,  54. 


B. 


BAIRISCH  BEER,  21. 

Barber-surgeons  of  England  and  Ger- 
many, 67. 

Bath-sponge,  advantage  of  using,  46. 

Bath,  Turkish,  arguments  in  favour  of, 
104;  injurious  effects  of,  103  5  warm, 
in  France,  90. 

Battle  of  physiologists,  17. 

Beer,  use  of,  as  food,  21 ;  absorption  of, 
42. 

Bees  convert  sugar  into  fat,  23. 

Bell  in  an  air-pump,  150. 

Belly.  See  Abdomen,  11,  12;  and  the 
members,  29. 

Bernard,  M.,  experiments  of,  on  use  of 
pancreas,  40  ;  saliva,  33. 

Berthelot,  discoveries  of,  13. 

Bile,  experiments  on  use  of,  38 ;  com- 
position of,  39  ;  duct,  38 ;  use  of  the, 
ib. ;  where  formed,  37. 

Biology,  derivation  of  the  term,  27. 

Bird,  experiments  on,  with  carbonic 
acid, so ;  hydrogen,  81. 

Bladder-gall,  38  ;  urinary,  102. 

Blade  bones,  9. 

Blood,  circulation  of,  47—69 ;  clot  of, 
47;  coagulation  of,  ib. ;  colour  of  ar- 
terial and  venous,  49;  views  of  Ber- 
nard on,  ib.  ;  composition  of,  48  ; 
corpuscles,  use  and  death  of,  50 ;  form 
of,  47 ;  passage  of,  into  capillaries, 
5-2;  quantity  of,  in  man,  48;  con- 
sumed per  annum,  81;  serum  of,  4/  ; 
temperature  of,  90 ;  views  of  Liebig 
on,  49. 

Blubber,  quantity  of,  eaten  by  Esqui- 
maux, 23. 

Blue-pill,  how  long  remains  in  the  sys- 
tem, 26. 
Bones.     See  Skeleton,  7,  8. 

Brain,  conclusions  of  Wagner  regarding, 
119;  diseases  of,  117;  grooves  of,  114, 
118;  of  man,  smaller  than  that  of 
elephant,  119;  proper,  exact  use  of, 

2 


164 


POPULAR  PHYSIOLOGY. 


117;  quantity  of  grey  matter  in,  at 
different  ages,  118;  relation  of,  in 
man  (as  regards  size)  to  its  tieryes, 
119;  man's  to  that  of  apes,  ib.;  ver- 
tical height  of,  120 ;  weight  of,  in  both 
sexes,  119. 

Bread  made  in  Denmark,  27 ;  and  water 
diet, t A. 

Breath.    See  Respiration,  "0. 

Breathe,  the  reason  why  we,  82. 

Bronchial  tubes,  72. 

Broncnitis,  89. 

Broth,  nutritious  property  of,  26. 

Brunner,  glands  of,  36,  3/. 

Buffalo- licks,  where  found,  24. 

Butter,  acid  of,  in  gastric  juice,  35 ; 
produced  by  rheumatism,  97;  re- 
tailers, practice  of,  23. 

C. 

C^SALPINUS,  discoveries  of,  69. 
Calmuc  and  Kaffre,  skulls  of,  126. 
Canal  digestive,  structure  of,  34. 
Canals,  semi-circular,  of  ear,  148. 
Canine  teeth,  31. 
Capillaries,  by  whom   discovered,  69; 

derivation  of  the  word,  50  ;  where  the, 

lie,  ib. 
Carbonic  acid,  action  of  on  albuminate 

of  iron,49 ;  ditto  on  blood,  ib,;  influence 

of  on  life,  81. 
Carnivora,  length  of  intestine  among, 

41. 

Carpenter,  Dr.,  quotation  from,  151. 
Cataract,  141. 
Cell,  what  is  a?  17;  theory,  explosion 

of,  17, 18 ;  white,  of  the  blood,  49. 
Centigrade  thermometer,  90. 
Centre  of  gravity,  108. 
Cerebellum,  114;   function  of,  121;  of 

pigeon,  experiments  on,  ib. 
Cerebrum,  114,  115,  118,  119- 
Cheese,  what  it  is,  how  differs  from  al- 
bumen, formation  of  from  milk,  23 ; 

of  vegetables  used  by  Chinese,  24. 
Chest,  structure  of,  73,  74. 
Chewing  of  food,  32. 
Chord,  spinal,  115. 
Chord,  vocal,  84;    use  of,  length  of, 

position  of,  85,  86. 

Choroid  coat,  use  and  structure  of,  133. 
Christiana  beer,  2. 
Chyle,  44. 

Cilia,  use  and  form  of,  72,  "3. 
Ciliary  muscle,  135. 
Circulation  of  blood,  discovery  of,  68, 

69  ;  in  capillaries,  58 ;  proof  of,  64,  65, 

66 ;  rapidity  of,  61 ;  who  coined  the 

term,  69. 

Clay  mixed  with  food,  27. 
Cleanliness,  benefit  of,  46. 
Clothing,  waterproof,  why  oppressive, 

Coagulation,  nature  of,  48. 


Coccyx,  8. 

Cochlea  of  ear.  148. 

Coffee,  use  of,  as  food,  25. 

Cognac,  beneficial  effect  of,  21. 

Cold,  are  we  ever,  91. 

Collar  bones,  9. 

Colour-blindness,  138  ;  cause  of,  ib. 

Colours,  primary,  ib. 

Combustion,  nature  of,  92  ;  classifica- 
of  food  in  connection  with,  ib. 

Concha  of  ear,  146. 

Consumption,  or  Phthisis,  89. 

Consumptive  children,  peculiarities  of, 
22. 

Coracoids,  9- 

Corns,  growth  of,  96. 

Cornea,  structure  of,  133. 

Correlation  of  forces,  illustration  of  the, 
13. 

Coughing,  88. 

Cranium,  9. 

Creator,  necessity  for  admitting  exist- 
ence of,  5. 

Cricoid  gristle,  84. 

Crystallization,  resemblance  of,  to 
growth,  15. 

Cuticle,  position  of,  95. 

D. 

DAW,  Sir  H.,  anecdote  of,  154. 

Death,  apparent,  case  of,  15,  16;  soma- 
tic and  molecular,  15. 

Decomposition,  a  proof  of  death,  16. 

Deglutition,  42. 

Denmark,  peat-formations  of,  127. 

Dentine  of  teeth,  31. 

Derma  of  skin,  95. 

Development,  meaning  of  the  term,  18; 
of  lower  plants,  14  ;  of  sinew,  18. 

Diaphragm,  action  of,  76. 

Diarrhoea,  from  using  gelatine,  52. 

Diatomacese  as  food,  27. 

Diffusion,  mutual,  77,  78. 

Digestion,  29;  organs  of,  31,  32. 

Distinction  between  plants  and  animals, 
2. 

Division  of  natural  objects.  ,1 . 

Dogs,  experiments  on,  with  sugar,  2". 

Drowning,  how  takes  place,  70;  re- 
markable case  of,  16. 

Drum  of  ear,  147. 

Duchek,  experiments  of,  on  alcohol,  21. 

Dyspepsia,  derivation  of  the  word,  46. 

E. 

EAR,  external  and  internal,  147,  148. 

Eggs,  composition  of,  23. 

Elements    and  words,    analogy  of,   2 

nature  of,  ib. ;  number  of,  ib. 
Enamel  of  teeth,  31. 
Endosmose,  4. 
Epidermis,  95. 
Epiglottis,  84. 


INDEX. 


165 


Esquirol,  M.,  opinion  of  phrenology,  125. 

Estimate  of  man's  architecture,  7. 

Ether,  evaporation  of,  99- 

Ethnology  of  skulls,  125,  127 . 

Eustachian  tube,  149. 

Exosmose,  4. 

Expiration,  /6. 

Eye,  the,  132;  ciliary  muscle  of,  137; 
coats  of,  humours  of,  134,  135 ;  dis- 
eases of,  141 ;  focusing  power  of,  137; 
formation  of  images  by,  136;  lids, 
lashes,  and  brows  of,  140  ;  muscles  of, 
133 ;  pupil  and  iris  of,  135. 

F. 

FABRICIUS,  discovery  of,  69. 

Fahrenheit's  thermometer,  90. 

Faraday,  Professor,  domain  of,  91. 

Fat,  when  digested,  35,  36 ;  use  of,  as 
food,  22. 

Feathers  and  teeth,  relatives,  32. 

Fibrine,  action  of  ammonia  on,  48 ; 
bearing  of,  on  medical  jurisprudence, 
ib. ;  network  of,  ib. ;  relation  of  to 
albumen,  ib. ;  use  of  in  blood,  ib. 

Fire-king,  the,  94. 

Flesh,  structure  of,  109 ;  when  digested, 
35. 

Food,  classification  of,  20 ;  definition  of, 
19;  one  form  of,  experiments  with, 
27 ;  quantity  of  required  per  diem,  46 ; 
time  required  for  digestion  of,  45  ;  to 
digest,  what  we  require,  29. 

Forces,  correlation  of,  13. 

Force,  vital,  12. 

Freezing  of  maggots,  the,  94. 

Friction,  production  of  heat  by,  93. 

Furnace-function  of  lungs,  92. 

Furrows  on  the  fingers,  96. 


G. 


GALKV,  discovery  and  period  of,  68. 
Gall-bladder,  38. 
Ganglion,  what  is  a,  116. 
Gastric  glands,  35 ;  juice,  ib. 
Gelatine,  use  of  as  food,  25. 
General  practitioners  of  England,  67. 
Germ,  action  of,  on  air  and  water,  14. 
German  barber-surgeons,  68;  theory  of 

cells,  1", 

Girdles,  locomotive,  9. 
Glands,  what  are,  30. 
Glass  pounded,  a  poison,  26. 
Gravel,  102. 

Gravity,  centre  of,  108,  109. 
Groux,  M.,  breast-bone  of,  63. 
Grove,  Mr.,  views  of,  on  force,  13. 
Gullet,  30. 

H. 

HAMBURG  WHALER,  experiences  of,  23. 
Hammer-bone  of  ear,  148. 


Harvey,  discoveries  of,  6s ;  simile  of, 
62. 

Heads,  round  and  long,  125. 

Hearing,  organs  of,  146. 

Heart,  auricles  and  ventricles  of,  53; 
expansion  of,  56  ;  form  and  structure 
of,  52,  53 ;  force  of,  57 ;  force-pump, 
action  of,  56 :  impulse  of,  63 ;  rhythm 
of,  61  ;  sounds  of,  62,  63. 

Heat,  action  of  on  solids  and  liquids,  93 ; 
animal  development  of,  92;  great, 
power  of  resisting:,  94  ;  influence  of 
nerves  upon  production  of,  ib. ;  latent, 
meaning  of  the  term,  99  j  maintenance 
of,  93;  nature  of,  91. 

Heel,  action  of  in  walking,  108,  109. 

Heel,  bones  composing,  10. 

Hiccups,  90. 

Hot  and  cold,  why  we  feel, » b. 

Humboldt,  and  people  of  Oronoco,  27. 

Humours,  vitreous  and  aqueous,  135. 

Hunger,  cause  of,  27 ;  production  of  in 
different  animals,  28. 

Huxley,  Professor,  lectures  of,  127. 

Hygiene,  81. 


IDEAL  VERTEBRA,  7. 

Ilia,  9- 

Incisor  teeth,  31. 

Indians,  American,  perception  of  sound 

by,  151 ;  Peruvian,  nasal  powers  of, 

143. 

Ingoldsby  legends,  lines  from,  64. 
Insane,  power  of  the,  to  remain  without 

food,  28. 

Inspiration.    See  Respiration,  70. 
Integument,  II,  95,96. 
Intelligence,  indications  of  in  brain,  34. 
Intestines,  ib. ;  length  of  in  sheep,  41 ; 

in  man,  ib. 

Iris,  use  and  structure  of,  ib. 
Iron  in  the  blood,  49. 
Ischia,  9. 
Isthmi-faucium,  42. 

J. 

JAUNDICE,  38. 

Jaw,  movements  of,  32. 

Jellies,  value  of  as  food,  26. 

Juice,  intestinal,  36 ;  experiments  on,  37 

K. 

KIDNEYS,  the,  100  ;  membranous  canals 
of,  1 02 ;  microscopic  anatomy  of, 
101 ;  secretion  of,  102. 

Knowledge,  what  consists  in,  12. 

L. 

LACHRYMAL  GLAND,  141. 
Lacteal   absorption.      Views     of    two 
schools,  44,  45  j   trunks  and  leaflets, 

44. 


106 


POPULAR  PHYSIOLOGY. 


Lacteals  in  the  dog,  experiments  show- 
ing, 45. 

Lactic  acid,  of  perspiration,  97 ;  experi- 
ments with  on  dogs,  98. 
Larynx,  84. 

Lassaigne,  experiments  of  on  saliva,  34. 
Lateral  ventricles  of  brain,  114. 
Laughter,  production  of,  88,  89. 
Lens  crystalline,  135. 
Lenses,  action  of  on  light,  129. 
Levers,  varieties  of,  106. 
Lewis,  G.  H.,  on  gelatine,  25. 
Liebig,  Baron,  views  of,  on  alcohol,  22 ; 

on  beer,  21  ;  on  blood,  49. 
Life,  nature  of,  12. 

Light,  concealment  of  by  plants,  13. 
Lighthouses  built  on  a  common  plan,  7. 
Light,  rays  of,  laws  regulating,  12Q. 
Lights.-    See  lungs,  71- 
Limbs,  how  moved,  106. 
Lithotomy- stool,  104. 
Liver,  structure  arid  use  of,  37,  38. 
Locomotion,  106;  in  girdles,  9. 
Lower  plants,  development  of,  14. 
Lung,  structure    of,  71 ;    use  of,  79  ; 

lobules  of,  71. 
Lytton,;sirE.  B.,  "Strange Story" of, 1 6. 

M. 
MAGKNDIE,  experiments  of,  on  dogs, 

27. 

Malpighi,  discoveries  and  period  of,  69 
Mammals,  what  are,  24. 
Man,  early  races  of,  126;  pre-historic 

age  of,  127. 

Mara,  Madame,  voice  of,  86. 
Mariners,  shipwrecked,  hunger  among, 

23. 

Marrow,  spinal,  116 ;  function  of,  122. 
Mastication  of  food,  32. 
Matter,  indestructibility  of,  13. 
Meals,  propriety  of  resting  after,  46. 
Meat,  decaying,  action  of,  on  sugar,  15 
Mechanism  of  man,  method    of   exa 

mining,  5. 
Medulla  oblongata,   114;    function  of 

121. 

Melancholy  and  bile,  38. 
Melt,  or  spleen,  104. 
Membrane  supporting  intestine,  41. 
Membranes  of  the  brain,  114. 
Mental  faculties,  118. 
Mercury  no  poison,  26. 
Meridian,  ethnologic,  126. 
Milk,  composition  and  use  of,  24. 
Minerals,  use  of,  as  food,  24 ;  required 

as  food,  ib. 
Mitral  valves,  55. 
Molar  teeth,  31. 
Motion  and  Locomotion,  106. 
Motion,  nerves  of,  122. 
Mucus  of  intestine,  35. 
Muscle,  action  and  contraction  of,  110 

structure  of>  102. 


Musk,  perfume  of,  144. 
Mycetes,  larynx  of,  86. 


NAPOLEON'S  opinion  of  phrenology,  125. 

<Tasmyth's  steam-hammer,  86. 

^ephrophagous,  derivation  of  the  word, 
103. 

Nerve  of  hearing,  148:  of  sight,  133;  of 
smell,  143;  sympathetic,  116;  of  taste, 
144. 

Nerves,  termination  of,  122,  123;  of  the 
intestines,  41 ;  sensory  and  motor,  dis- 
tinction of,  123. 

Nervous  system,  111 — 125;  ami  life  re- 
lated, 111  ;  matter,  structure  of,  113. 

Network  of  blood-vessels  in  frog's  foot, 
65;  in  kidney,  101;  offibrine,  48. 

Nicotiana  tabacum,  28. 

Nicotine,  ib. 

Nightshade,  deadly,  action  of  on  lung, 
73. 

Nitrogen,  use  of,  in  air,  80—83. 

Nostrils,  142. 

O. 

OTL  OF  TOBACCO,  28. 

Olfactory  lobes,  114. 

Optic  nerves,  133. 

Optics  of  the  eye,  129. 

Organization,  meaning  of  the  term,  14. 

Organs,  definition  of,  5. 

Orthognathous  skulls,  126. 

Oscillation  in  walking,  cause  of,  109. 

Oven,  reason  why  a  man  can  enter  with 

safety  an,  99. 
Oxygen,  action  of,  on  phosphorus,  80 ; 

use  of,  79- 
Ozone,  action  and  composition  of,  80. 


P. 


PACINIAN  CORPUSCLES,  152. 

Pancreas,  40. 

Pancreatic  juice,  40;  experiments  on, 

ib. 

Papillae  of  skin,  96;  tongue,  98. 
Parts,  soft,  of  man,  10. 
Pastrycooks,  labours  of,  22. 
Pepys,  Samuel,  and    barber- surgeons, 

67. 
Perspiration  glands,  form  and  number 

of,  96,  97 ;  fluid,  composition  of,  97. 
Perspire,  how  we,  98. 
Peyer,  glands  of,  36. 
Pharynx,  4 1 ;  and  nostril  communication 

between,  83. 

Phosphorus,  action  of  oxygen  and  nitro- 
gen on,  80. 
Phrenology,  errors  of  and  objection  to, 

123—125. 
Physiology,  importance  of,  to  physician, 

64     derivation  of  the  term,  16. 


INDEX. 


167 


Pigment  of  the  eye,  133. 

Pivot  of  levers,  106. 

Plan,  general,  of  skeleton,  104. 

Plants,  benefit  of,  to  man,  2;  temper- 
ature  of,  by  day  and  night,  93. 

Platinum,  powdered,  action  of,  on  oxy- 
gen, 14. 

Pleura  of  lung,  71. 

Poison,  what  is  a,  26. 

Poles,  barbers',  meaning  of,  6" ;  ethno 
logic,  126. 

Porter,  Dublin,  composition  of,  21. 

Potatoes,  absorption  of,  42,  43. 

Power  of  levers,  106. 

Prehension,  10. 

Principle,  vital,  12. 

Principleists,  school  of,  16. 

Prism,  effect  of  on  rays  of  light,  131. 

Prismatic  spectrum,  132. 

Prognathous  faces,  126. 

Protective  skeleton,  8. 

Pubes,  9. 

Pulse,  beats  of,  number  in  different  ages, 
6l ;  cause  of,  59;  influence  of  mind 
over,  60. 

Pupil  of  the  eye,  135. 

Pyramidal  gristles  of  larynx,  85. 

Pyropathy,  meaning  of  the  term,  103. 

Q. 

QUININE,  smallest  particle  of,  that  can 
be  tasted,  146. 

R. 

RACES  of  man,  126,  127. 

Raw  material,  weaving  of,  as  food,  39. 

Reflex  actions,  nature  of,  J  22. 

Refraction,  ib. 

Reptiles,  effect  of  hunger  on,  28. 

Respiration,  function  of,  70 — 80  ;  influ- 
ence of  external  impressions  on,  83. 

Rest,  why  bodies  remain  at,  108. 

Retina,  structure  and  use  of,  134 ;  para- 
lysis of,  139. 

Rheumatism,  cause  and  prevention  of, 
97, 98. 

Ribs,  movement  of,  /5,  76 ;  of  belly,  8 ; 
of  chest,  ib. ;  of  neck,  ib. 

Rickets,  from  what  it  proceeds,  24. 

Roots  of  nerves,  122. 

Russian  Tartary,  line  drawn  from  to  the 
Bight  of  Benin,  126. 

Russians,  predilection  of,  for  grease,  23. 

S. 

SALIVA,  action  of  on  starch,  34  ;  expe- 
riments on,  33  ;  influence  of  mind  over 
secretion  of,  34 ;  quantity  of,  secreted 
in  24  hours,  45  ;  quantity  of,  required 
for  various  kinds  of  food,  34 ;  use  of, 
33. 

Salivary  glands,  32,  35. 

Salt,  importance  of  as  food,  24. 


Salts,  decomposition  of,  produces  heat, 

93. 

Sanguis,  journey  of,  63—65. 
Schiller  on  the  four  elements,  22. 
Sciences,  other,    relation   of    to  phy- 
siology. 

Sclerotic  coat,  structure  of,  133. 
Scrofula  prevented  by  sugar- eating,  22. 
Secretions,    glandular,    quantity  of  in 

24  hours,  45. 

Seeds,  influence  of  heat  and  light  on,  13. 
Semilunar  valves,  55. 
Sensation,  nerves  of,  123. 
Senses,  the,  128—155. 
Servetus,  discoveries  of,  69. 
Sighing,  cause  of,  88. 
Sign  of  German  phlebotomists,  67. 
Sight,  long  and  short,  138;  organ  of, 

132.- 

Sinew,  a,  development  of,  18. 
Skeleton,  general  character  of,  7 — 10. 
Skin,  structure  and  thickness  of,  95. 
Skull,  vertebrae  of,  9. 
Skulls,  shape  of,  among  various  nations, 

125, 126. 

Smell,  sense  of,  142,  143;  nerve  of,  ib. 
Smith's,  Sidney,  recipe,  91. 
Sneezing,  how  performed,  88;  sobbing,  ib. 
Soda  and  iron,  albuminate  of,  4Q. 
Sound,  nature  and  production  of,  149, 

150;  pitch  of,  151  ;  reception  of  by  the 

ear,  149 ;  vibration  of,  151. 
Sounds  of  heart,  imitation  of,  63. 
Spectrum,  solar,  131. 
Speculations,  impropriety  of  forming,  12. 
Speech,  organs  of,  87. 
Spinal  chord,    division  of,    115;    grey 

matter  of,  116. 

Spirits  of  salts  in  gastric  juice,  35. 
Spirometer,  78. 

Spleen,  function  of  the,  104,  105. 
Sponge-bath,  advantage  of  using  the, 

46 ;  related  to  man,  2. 
Spot,  vital,  where  situate,  121. 
Stammering,  cause  of,  87. 
Stark,  Dr.,  death  of,  27. 
I  Stereoscope,  explanation  of,  139- 
\  Stethoscope,  150. 
Stirrup-bone,  148. 
Stomach,  34. 

Strychnine  the  food  of  a  bird,  27. 
Sugar,  passage  of,  by  endosmose,  4; 

formation  of  by  liver,  38. 
Suction,  experiments  on,  75. 
Sulphur  of  bile,  absorption  of,  40. 
Sweat-glands,  character  of,  96 ;  number 

and  action  of,  97. 
Sweetbread,  characters  of,  40. 
Sympathetic  system,  116. 

T. 

TASTE,  organs  of,  144  ;  varieties  of  146. 
Tea,  use  of,  as  food,  25. 
Tear- gland,  141. 


1G3 


POPULAK  PHYSIOLOGY. 


Tears,  secretion  and  use  of,  141. 
Teeth,  number,  structure,  and  variety 

of,  31. 

Teetotalism,  absurdities  of,  20. 
Theatre,  German,  accident  in,  68. 
Thorn-apple,  action  of  on  lung,  73. 
Thorax,  73,-  74. 
Thymus  gland,  105. 
Thyroid  gland,  105  ;  gristle,  83. 
Tissue,  what  is  a,  17. 
Tobacco,  effects  of,  on  the  system,  28. 
Tongue,  144. 

Torricelli's  explanation  of  suction,  75. 
Touch,  organs  of,  and  experiments  on, 

151,  155. 
Townsend  Col.,  influence  of,  over  his 

heart,  64. 

Trachea,  or  windpipe,  /!• 
Tree-lacteal,  the,  44. 
Tricuspid  valves,  55. 
Turkish  Bath,  action  of,  103. 
Tympanum,  147. 
Typical  vertebra,  7- 

U. 

UREA,  where,  is  formed,  102  5  conver- 
sion of  gelatine  into,  26. 

Urine,  composition  of,  102  j   secretion 
of,  t A. 

V. 

VACUUM,  nature  of,  75. 
Valves,    neutral,  55 ;     semilunar,    ib. ; 
tricuspid,  ib. ;  of  veins,  50,  58,  59. 


VaroliiPons,  115. 
Vegetables,  action  of,  on  air,  3,  14. 
Vegetal  division  of  organs,  10. 
Ventilation,  importance  of  attention  to, 

81,  82. 

Ventricle  of  heart.  54. 
Ventricles,  lateral,  of  brain,  114. 
Ventriloquism,  views  as  to  thenature  of, 

87. 

Vertebrse,  7- 
Vertebral  column,  8. 
Vesali  us,  discovery  and  misfortunes  of, 

68. 

Vestibule  of  ear,  148. 
Villi,  what  they  are,  35,  44. 
Vinegar,  in  gastric  juice,  35. 
Voice,  organs  of,  83 — 87 ;   compass  of, 


W, 

WAGNER,  researches  of,  upon  the  brain, 

119- 

Walking  (see  Locomotion),  108,  109. 
Water,  action  of  heat  on,  98,  99. 
Warm-blooded,  90. 
Watch,  comparison  of,  with  man,  5 
Weight,  our  conceptions  of,  154. 
Wheel-animalcules,  boiling  of,  94. 
Whistling,  8~. 
Wind-pipe,  70,  73. 


Y. 


YAWNING,  88. 


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